The cost thing... is a hard question to answer. It depends greatly on what car you decide to run, what needs done to it, how thorough you are, how many upgrades you do... etc.
I'd say as a general rule, expect to spend $5k to get a car, and fully prep it for the first season of racing. During the season, expect to have to put a decent amount of money into it to maintain it, replace broken parts, etc.
Some parts you'll need:
Car itself
cage (I can't recommend enough how much more worthwhile it is to have someone weld in a cage - bolt in cages are a pain and not as safe)
seat/bracket/belts
motor 'freshening'
replacing worn/tired suspension, driveline and steering components
brake calipers/rotors/pads - get pads that will hold up to some decent heat and track racing
Wheels
tires (dunlop Star specs if you want to be competitive)
Personal safety gear - sky is the limit but Helmet, suit, underwear, gloves, socks, shoes, and I recommend a HANS type device.
Tools and spares to bring to the track - as luck dictates the more you bring the less problems you have
Tow vehicle and trailer to bring the car to the track
Parts vehicle?
also, the 2012 schedule will be out in a month or so.