the wear and tear is not bad. you hardly ever see cars breaking on track. you really just use tires, break pads/rotors, and put a little stress on the power steering systems if you run a lot of RPM's. you don't shift much so the trans isn't too stressed.
with my car being heavy i did go through 2 power steering pumps before i figured out it was too much heat and rpm's for the pump though. i had to add a 24 inch long finned Derale power steering cooler that holds an extra quart of fluid in the system and put a bigger pulley on the power steering pump to keep the RPM's lower. it has been rock solid since.
Good to know, I guess since the autocross track is so compact, you aren't constantly going through the the gears and really stressing the engine and trans. Make sure to post some pictures and videos in here the next time you go
I think someone else in here did autocross too, I want to say it was Air Spider in his old SRT Jeep, I may be wrong though.