They should place you with the lowest class, but don't presume they weed out morons. The SAAC events scare the hell out me (versus other events) because they sometimes let folks from faster classes intermingle in for more track time, and I've witnssed them letting in folks for the historic race events "practice" among the open track groups (had some TransAm Mustangs zooming by me a few times on the high banks at Fontana...passing on the wrong side, etc.)
Just keep your own pace and follow the rules re acknowleging passes with hand signals, etc.
Double throttle return springs, make sure your battery is tightly fastened down, no big leaks, a puke tank for your coolant (check out the plastic ones at Summit if you don't want to do anything permanent), double-check your hoses and belts, make sure your tires are in good shape, make sure your helmet is new enough (full face despite me getting away with an open face at the Bash), check your seatbelts...no frays and correctly/tightly fastened, tape the lights, safety wire what needs to be, run water only in the cooling system (a little WaterWetter won't hurt), leave nothing behind the seats or in the trunk...
...and then, crawl under the car and tighten every damn bolt. When you're done...do it again.
An open track event or two would be an excellent idea!
Then tighten everything again.
Take tools and replacement items: plugs, belts, hoses, fuel pump, brake fluid,
oil, water, a 10 gallon air tank and a damn good gauge, extra water for the cooling system, jack/jackstands/chuks, etc.
Then tighten everything again.
