You will receive a notice of receipt for the form stating that "Your alien card is extended one year - employment and travel authorized". Keep the receipt with your green card. If by some chance you are not approved within a year you will want to make an InfoPass appointment to go to your Local Office to request an I-551 stamp in your passport. This does happen as it sometimes it takes over a year to be approved. After your NOA extension expires, this is your only evidence of legal status which you are required to have, by law. This happens occasionally, that a case takes over a year, but it's rare. Local Offices will not give an I-551 stamp is you have another type of evidence of status (ie, expired Green Card + extension letter).

I am starting to research the whole lifting of conditions process as I will be able to file my I-751 in a few months. Looking at the time lines and other posts it seems clear that my existing 2 year GC will expire before I am issued with a 10 year GC. I have read that the USCIS effectively extends your PR status for 12 months while the I-751 is under review but will I be able to travel abroad with just the expired GC and the I-751 NOA, or is Advanced Parole needed to prevent troubles at the POE on return?

Thanks!