1. Wheels - Depends on use, style, and how much willing to spend. I didn't want to affect the speedo so stayed with the stock diameter on 17" rims and BFG KO2 tires vs. our stock 4X 16's. Here's a wheel/tire/offset calculator to compare against stock. Several of our sponsors have wheel and tire options
2. Stereo - Crutchfield has just about everything you need that fits. Back up cams can be found fairly cheap on Am*zon. Again, depends on budget, what kind of sound you are looking for
Add some specifics to what you are after and folks can chime in - note opinions will vary. Good luck in your search.