N400Applier,
I had received IV letter in about 2 months after FP and the interview was about a month later. Total process took about 4 months.
Documents needed are Green card, Passport and ID(Drivers License) for proof of residence. For me the officer also asked a copy of marriage certificate(dono why?), for which I had to go across the street and make copy and submit later same day before oath.
My wife did not have a drivers license, so she was asked 2005 tax documents for proof of residence in Maryland.
Everything went smooth, most of the officers are courteous enough to help.
All the best to you all again.