I hope you'll come out and give it a try.
A helmet is nice to have (needs to be Snell-rated), but if you don't have your own there are loaners available.
Renoscca.com used to have a Newbie's guide linked somewhere, but I can't find it now. But, the following does have some useful information as well:
http://www.tirerack.com/features/solo2/handbook.htm
Assuming you may want to start out in our novice class, you can participate in the morning or the afternoon. If you run in the morning you should get there no later than 8-8:30, to register, unload your car & get it through the tech inspection, and have enough time to walk the course. For the afternoon session, get there by 11-11:30.
You will drive in one run group, and be a course worker in the opposite run group. (You'll be shown the ropes on what to do as a course worker.)
Once you're serious about competing for season points - there is a scheduled time you need to be there for the car class you are in. For example, this Saturday all street tire class cars run in the afternoon; and on Sunday they run in the morning.