1-going to (hopefully) doing time atack
2-buy lots of books on racing technique and go hone you skills with a crappy car. (adaptation is the best)
3-unless you have hookups or decent sponsors it can be VERY expensive if you want to race competitively, but is fairly cheap if your a weekend tracker.
4-some sponsors get very involved and will go to the track and keep a lookout on things, others may just wright you a check and forget your name.
5-as many races as there is for the series.
6-if you havent built the car, you can build a car to the class you want to join. cost is how much money your willing to put into it and how much you get for sponsors. the time spent traveling to the track can be great, but is usually worth it for two day or week long events. well if you dont like racing then why are you asking? usually fixing the car isnt bad because its almost always fallowed by something breaking that wasnt meant to break, but when you blow a motor or something like that, its a bummer.
7-as for items to tote around to the races, spares, tools, radios, food, crew, car, kid on a motorcycle to make that 5 minute trip to autozone at the last second.
its fun though, especially when you dont whine and complain everytime something goes wrong..