[DonC]

Sal:
Autocross and local track days should just about cover you without really having to change the car unless you get bitten by the "competitive" but, then all bets are off.
Autocross will let you know what it feels like just before and just after the car lets go without doing any significant damage other than your pride. Autocross is very fast so it will also really help with your reaction time. People can say all they want about dashing around a parking lot but don't kid your self. You really have to have your head out because there's very little room for error.
To really wring the car out (within your limits of course) hook up with a couple of local track days a year. You won't be "racing" with anyone but it does give you a chance to put the car through it's paces while minimizing the chance of a shunt into another driver. A shunt off the course is, however, up to you and how far you push yourself.
If you start seriously Autocrossing and then move to the open track you may find yourself wondering what the heck to do with all the spare time you have on those straights.
Start slow until you get to know what the car is going to do in a specific environment the build up gradually. Either discipline will take all of your money and all of your spare time if you let it which is just what a good hobby is supposed to do.
DonC