One stud shouldn't be a problem, but the tech inspection people would have probably complained if they saw it.
The club that holds events at Giants Stadium does a few autocrosses on Friday afternoons from 3pm until sunset. Here's their schedule:
http://autox4u.com/MSNE/index.htm. And the Englishtown events shouldn't be so bad for you since you won't have to drive an hour.
Enkeis are fine. You'll only have problems with pot holes if you run super low profile tires.
Some pictures from yesterday:
Me with the rocket start lol:
Dat locking up the left front... not used to garbage tires:
Modified by mirochuki13 at 5:03 PM 3/24/2008
Modified by mirochuki13 at 5:05 PM 3/24/2008