Well there is a chance that the application gets forwarded to CSC instead of your local center. And in most cases there is no interview. Green card is issued but at 5-8 months.
Then if you get an interview, you would have to show up at your closest USCIS interview center and answer questions about your relationship. Then the green card is granted at interview, you get the card within a couple weeks.
The number should be an MSC number...and you can track it like the old number. If you filed for AP or EAD, then you would get numbers for those too. Usually granted sometime between 2 - 3 months after applying.
