The only thing you need to do before hitting the Ring is get the 1,200 mile service done. As a first timer, you'll be considered fast if you can complete a lap in 10 min. At that pace, you will not be stressing the M3 at all. I wouldn't worry about the car, start learning the corners now. If nothing else, read up on how to properly enter into Adenauer Forst. That is the one that bites the most people in the ass.