You don't need driving school for SCCA events...
From what the rules you are stating it doesn't sound like it is an SCCA event.
Event schedual looks pretty typical. Usually we bump everything back by about an hour and have first car out around 9 ish.
Honestly I would drop the coin for the membership, then go and have fun. Yes a drivng school will make you more competitive but honestly I had the time of my life and I was running decent close to the cars in higher classes than I was in.
I always like to have someone in the car with me critiquing my run and showing me where to go slower, faster stuff like that except on my last 2 runs. Hell one run we had 4 guys in my friends STi. That was fun.
You don't have to do everything to win. I had tons a fun, came in First in class a couple times but for the most part was mid pack overall which I was happy with.
You are 18 so you wont need a parent with you, the membership thing kinda sucks but if it isnt too expensive I would just go ahead and buy it and go out and have some fun. if they are designating you as a novice driver they probably have a novice class. If not you are kinda screwed on winning cause of your turbo upgrade. If they use SCCA classes that puts you in Street Modified (SM) which most well prepped cars are usually runnning decent HP numbers and a boatload of suspension, R-compound tires and so forth.
To make my long post short, drop the coin for the membership, go out and have fun. You don't need a full fledged driving school to have fun at Auto X. If you are skeptical go out one day and just hang out. talk to some people, most of the AutoXers are nice guys and if you ask them in their early runs they will let you ride along and then you can see if it is really something you will enjoy.
Typing this makes me miss my WRX and reallllly miss my evo. That thing shredded out at AutoX.
I need to buy a shifter cart so I can go out again.