I'm glad you're getting interested in tournament paintball. It's great. I'll try to answer your questions as you asked them.
I'd recommend starting in the lowest division possible, which usually depends on the tournament series. Most tournaments have a rookie division, or, if it is using APPA (Paintball ranking database), Division 5. It's easy to move up if you find that you're better than the division you start in.
To find a team and tournaments, you can look in the regional forum (http://www.pbnation.com/forumdisplay.php?f=518
) for local fields, tournaments, and teams. I would recommend talking with the people you play with at your local fields- talk to the owners, refs, and other players. They can usually point you in the right direction and help you find people you need to talk to.
The gear you have is all you need. I started playing tournaments with a Tippmann and did just fine.
Good luck with everything. Let us know if you have more questions.