Hi Mike,
WELCOME!
You'll find the 944-SPEC series very friendly to beginner and experience racers alike.
What Joe said, you'll need the 7" late offset (52mm) phone dial wheels. We tried stuffing a 7" early offset (23mm) cookie cutter onto a 924S to get a wider track and to use a lighter legal wheel but it didn't work.
I use to think you need a fully built out car (full suspension, engine, etc.) to race but I completely reverse my thinking after seeing how well some of our guys are doing starting off with essentially a stock car and just safety equipment. Seat time, getting use to traffic is more important, you can always finish the suspension when time and money permits.
I agreed with everything Lee said except the timing belt. For a $12 part it sure can cause a whole lot of damage if it breaks. I had a timing belt break on my first 944 (many years ago) and the results were seven bent valves, two damaged pistons and a damaged head.
So now that's the first thing I always change out when I acquire a unknown 944 whether its for street or track.
Good luck on the build out and go out there and have fun!