The answers to all your questions and even some you didn't know you had are here. Wheels & Tires: Everything you should need to know is in here. A Must Read!!!!!!!
I, along with many, many others, run 315/35/17's in the rear. Roll your fenders and they will fit. They WILL rub if you don't roll your fenders (maybe not in normal driving, but hit a big pothole or a big dip on the interstate, especially with weight, and they WILL rub).
I ordered my fender roller from a user on this forum. Total was around 70$ for all the shipping and such. Trans-Am something is his user name. I'm sure someone will jump in and clarify his name. Awesome user and provided great feedback to help me through the process.
EDIT: 69T/A is his user name