Good for you!!! I hate to not give you a more personal answer (coffee... heading to shower... off to work) but there's been a lot of good stuff written about Al-Anon meetings and what to expect; check out this thread:
http://www.soberrecovery.com/forums/...ings-like.html
And above all, don't worry. There are no musts in Al-Anon and nobody is going to force you to do anything! (((hugs)))