Yeah - definitely go with stock or silver can. You'll save a lot of time and frustration with broken parts if you start out a bit slower. It's way more fun to drive a bit more slowly, but keep your car in one piece for the day.
As the other guys said, most racers choose either a Stratus, Mazda 6, or one of the other Protoform bodies. It will give you the most even downforce and a good starting point. The sports car bodies look good, but don't have the same level of aerodynamic tuning. However, if you've only got sports car bodies, you should be fine to get started with those.
Other than that, here are a few other tips that come to mind for your first time on the track:
- Be careful with your radio. Don't leave it on in the pits and remember to use whatever frequency control system they have at the track (clips, etc.)
- Be careful when you pull out onto the track. Don't pull out into traffic. Watch out for super fast modified cars. Don't go the wrong way. Don't stop on the driving line.
- If you crash or spin out on the track in a precarious spot (like the straight) call out to the other drivers on the stand and let them know. Otherwise, they'll smoke into your car going full speed and both of you might break.
- Just be careful, and ask lots of questions. People will help out.
Overall - just have some fun and rip it up! Try not to take too may people out.