I see you live in MI, which is one of IHMSA's hot spots. I would suggest you contact Jeff Hunt, the MI state director, at litegun@charter.net. Let him know where you live, and he'll point you to the nearest match director.
The bad news is that the MI season is probably over. The good news is that this gives you the winter to get ready for the 2005 season. I'm not sure if any of the MI clubs are shooting AIR in the winter or not.
Concerning equipment, IHMSA has disciplines for virtually all types of handguns from air to centerfire. My suggestion is to take what you have, give the game a try, and go from there. Please do not be put off by some of the more specialized handguns you will see at a match. Many of us have been shooting steel for years and have built up our collection gradually over time.
You'll find out that 99.9999% of our members are the most friendly & helpful folks you'll meet.
Keep us posted on your progress!
Steve Ware