Lots of great advice given so far! The route I chose to go with my car was first to just drive it as is. For Autocross, DE's (driver's Education), Performance Driving Schools, even some Time Trialing a cage or roll bar is not required. Once you get your feet wet you can decide just how far into things you want to continue to go. The next step for me was a Race Version Roll bar, I got it used for $200. It is bolt in and has the ability to be upgraded later to a full cage.
You will find lots of links at our site, including rules, event dates, car classification tools, forums, etc. I hope to see you at an event soon! In fact, how about the March 17 Autocross?
All the Best,
Mark
PCA SDR AX Chair
Porsche Club of America | San Diego Region