Insulation, Radiant and Vapor Barriers - Insulating a garage

I live in the Chicago area and I'd like to insulate my attached garage this fall. The back wall and part of one side wall are already dry walled and insulated, per code. The ceiling is just dry wall, without any insulation in the garage attic. Ultimately, by next winter, I'd like to add heat to the garage. I have an old car I'm restoring and it gets too cold out there to work in the winter. I'll be using fiberglass bats with paper backing and putting up dry wall.

Three questions.

1. What R value should I use in the garage attic, and should it be paper backed or just fiberglass bats?

2. Is R 13 good enough for the walls?

3. Should I use a vapor barrier on the walls even with paper backed bats?

OK, I slipped in 2 questions into one! ;) Thanks for any help I can get.

Have you thought about cellulose?? Especially for the attic if its already drywalled!! It will save you lots of time. Buy enough bags to do the requested R value, I did know this. I was told I needed about 12" of cellulose in my attic of the house, I am sure 6" would be fine in the garage. Is there storage above or is there a living space??

My dad has a detached 2.5 car garage and he used r 19 I believe in his walls. He lives near the NY state border but on the PA side. It gets cold, but I guess Chic. might be a bit colder!!! :) He only has the traditional paper back insulation w/ no other form of vapor barrier.

I would think even w/ the unfinished part you could drywall it, drill a hole in the drywall and just blow in cellulose. There is an argument that cellulose is better but who knows! Then just patch the hole.

Good Luck