For the steering wheel controls, you'll need a steering wheel interface, which will be based on the brand of stereo you buy.
Pacaudio.com sells these.

For the radio itself to keep door chimes, you will need a $120 or more wiring harness. Its like a regular wiring harness, but it has a box with it. Pac sells these, but best buy, crutchfield and sonic electronix all sell them as well. The pac part number you need is C2R-GM24 (without bose or onstar)

Pac-Audio.com Product Search | iPod Integration for your car and More by Pac-Audio - Connecting you to the future Prix&ModelId=1569&Year=2007&YearId=18