Woah, slow down there. You're getting way ahead of yourself with talking about a "racing license". As an instructor, let me rein you in a little bit.
1) The S2000 will need a roll bar. Period. I won't get in one without it. Most any organization will require a roll bar in a convertible (unless it has a factory device like a roll hoop).
2) It's admirable and wise that you want to learn the limits of your car, but there's a big difference between what we call "High Performance Driving Experience" (HPDE) and "racing". HPDE is where you should start. NASA, Car Guys, Trackdaze, SCCA and several others hold HPDE's at various tracks. NJMP is probably the closest track for you, or maybe Pocono.
3) Beginner HPDE's will have a limited number of cars on the track and very restrictive passing rules (such as only on the straights) in the beginner levels. Once you learn and can show you have good car control and situational awareness, you can move up to another group with less restrictive passing. It's a graduated system and helps beginners progress in a safe manner.
4) Wheel to wheel racing is not for street driven cars, and I also believe a driver should do several years of HPDE's before even considering going W2W racing. It's a whole other level of driving.
5) I'm not a fan of people buying fast cars to learn track driving. I'd rather teach a guy in a Miata than a guy in a Shelby Mustang any day, unless the Mustang guy has been doing it awhile. The more power, the more it can mask flaws, and also the faster you can get yourself into trouble. The S2000 is a nice car, but needs to be driven with a level of respect. I've seen plenty of them wrecked at the track by guys who didn't. Which brings us to:
6) Any car you take to the track, you should be prepared to walk away from. If it's your only car, and you owe a ton of money on it, don't take it. Most insurers will no longer cover you if you car is on a "racing surface", even if it's a "school". Bad things can happen at the track that aren't always under your control. All it takes is one broken radiator hose on the car ahead of you to dump coolant on the track, and off you go...into the tire wall.
It's a wonderful, addictive and very expensive hobby. I believe everyone should try it at least once, but do it intelligently.