how to pick a class to race in

Sounds like you should be running in the "Pro" class, although it is pretty cut throat! You can enter your car in more than one class if you like, and since you haven't been racing in a while, maybe start off in "Sportsman". You are bracket racing I assume, so you'll be dialing against your time trial times, not heads up against the other racers! Run as many time trials as you can to get the feel for your car, dial away and have some fun!! Geof