JasonGG

I agree, when my wife got her ADIT stamp, the Detroit office also took her expired GC.

And yes expect them to take your green card. Make a copy front and back before going to your info pass appointment. You will want that copy for your interview and N-400 process. 
 
If they  don’t take your gc, great 

Guess the field offices are different, here they take it and you get just the stamp and they tell you to come back with your passport if you need an extension.

They didn't take my wife's Green card.  They just placed the ink stamp in her passport and wrote the expiration date and her pending I-751 case/receipt number and the words "pending I-751".  They returned her passport and her expired Green card. 

Firstly you will need her passport, her expired green card (which they will take from her), your extension letter,an unexpired id card or driver’s license (for identification). The stamp is an ink kind of stamp just like the one she got when she arrived the USA (if she came with a cr1 visa). It will basically have the date of the day it is going to be stamped and it will be valid for a year. This is the moment for her to make copies of her expired green card for her record because they will take it away from
her during your infopass appointment. 

Similar things happened during our i751 case. We got 3 fingerprints notices, our i751 was approved after a combo interview 24 months or so after filing at naturalization interview. See our timeline below in the signature section below.

Looks like another USCIS mass error to me

See this thread 
Similar situation
 

@JessnTrev If you read the forum, multiple people had confusing messages about their biometrics today:
 
There appears to be a glitch in the system.

We called this morning for an infopass appointment at the Baltimore, MD office.  We were also told we'd get a call back in 30 days.  The email confirmation added that we'd get a text or email 1-2 business days before the call so we would be expecting it. - Jason

Looks good, but it's been a long time since we did the K-1 interview in HCMC.  We took copies of everything to the interview. Don't give them a giant pile of paper, but do give them an organized compilation of everything they ask for. I've been to the consulate a couple of times and successfully made it through the K-1. Some advice for the actual interview:
 
-Get there early and only take what you need. Leave your luggage and stuff at the hotel/home.
-Don't talk to people on the street near the consulate - a lof of scammers and bad actors.
-Don't look nervous while waiting to be called to the window. Smile. Be confident.
-The American can go to the window, but they may tell you to take a seat while they talk to fiance.
-Fiance needs to speak English and if she doesn't understand a question, tell them so.
-If you have anything that may be questionable or raise a red flag, be prepared to talk about it.
-Don't offer to explain anything they have not asked you about. Only answer the questions they direct towards you.
-Be nice. They hold the power.
 
We spent a lot of time inside the consulate watching interviews. And we know a lot of K-1 couples (Vietnam). If the American is present at the interview, it will be approved (unless something obvious is bad). You have to be prepared, but be real. Don't try to over-explain or get upset. You'll get through it OK.
Good luck!

Looks like your wife’s case was sent to NBC because she filed her N-400. Here on the forum a lot of people say that when you file for N-400 it can speed up the process of I-751, meaning that your wife may see progress with her applications probably sooner than later! 
I filed I-751 in September 2019, it sat at Potomac for almost 2 years and then in August 2021 they moved it to NBC. I am still waiting for an interview and I become eligible for N-400 in September 2022 (Divorce waiver). I think if I was able to file N-400 sooner, my case would have been processed by now and since your wife has already filed hers, it should be a faster processing! 

My wife's mother in her 60s got a US tourist VISA approved back in March with little issue.  Her wait time to get an interview was nowhere near 305 days.  Was about 100 days from the time she submitted the application.  Maybe the wait times are longer in Hanoi then Ho Chi Minh.  Mother owns a house in Ho Chi Minh worth about $700k with the father, has a lot of family in Vietnam, but no pension or retirement income (sounds pretty similar to your situation actually).  Her mother used a company over in Vietnam to help her with the VISA process.  I ended up writing a letter to support her visit.  
 
On the other hand, my wife's sister who is unmarried and in her 30s, has a job but owns no property, tried to get a VISA 6 months ago to visit my wife and was denied.  

MIL applied December 15th and interviewed March 3rd with 126 waiting days for her interview according to site  / 109 days later she had interview
if that helps u judge timelines 
 
 

according to USCIS wait time for interview for tourist visa is 305 days
 
https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/wait-times.html

This is not rocket science all they need to do is apply, agree their time one looks optimistic 

Yes.  My wife's son (12 at the time) interviewed at the consulate in HCM City with a family friend.  No issues at all.  As long as your step son has the correct interview documents and ID and the person accompanying them has a valid ID, a family member or friend can attend the interview with him in place of his mother.  They'll only allow one grandparent to accompany him inside the consulate.  It is not a difficult interview for minors.  Mostly just exchange greetings, a little small talk, and exchange of paperwork. 
 
Interview in HCM City is conducted with an American CO and an interpreter, so the interview can be conducted in English or Vietnamese.  Just make sure he understands the paperwork he is carrying so he can provide it when asked.
 
Best of Luck - Jason

Yes.  My wife's son (12 at the time) interviewed at the consulate in HCM City with a family friend.  No issues at all.  As long as your step son has the correct interview documents and ID and the person accompanying them has a valid ID, a family member or friend can attend the interview with him in place of his mother.  They'll only allow one grandparent to accompany him inside the consulate.  It is not a difficult interview for minors.  Mostly just exchange greetings, a little small talk, and exchange of paperwork. 
 
Interview in HCM City is conducted with an American CO and an interpreter, so the interview can be conducted in English or Vietnamese.  Just make sure he understands the paperwork he is carrying so he can provide it when asked.
 
Best of Luck - Jason

Yes

shouldnt be an issue as CBP can easily verify the  status 

I do not know for certain, but what you are talking about is the proof of her LPR status.  Proof of status can be either a 2 yr GC, an expired 2 yr GC with a valid extension letter, a 10 yr GC, or an expired 10 yr GC with the I90 receipt, so I would imagine any would work even if the approval of the new card has already been determined.  The only thing I can remember when my wife was at that stage was she could not use the entrance kiosks with an expired card.  You can try contacting the CBP office at the POE she will be re-entering to be certain.
 
Good Luck!
 
https://www.cbp.gov/contact/ports

My wife and her daughter filed in August 2020 and they have not received an extension letter.  Her son filed in May 2021 (arrived 6 months after her) and got an extension letter last week. - Jason

My wife filed 8/2 online.  Already received NOA1 and the letter saying they are reusing biometrics.  Initial estimate is 13 months.  Looking forward to having this final step of the long journey completed! - Jason

Just submitted the online application.

Hello my peeps....we are filing next week. Happy to be here.