Others will jump in here and share their own experiences with that first meeting, and I know a lot of ours will sound similar. I went to a meeting angry. Like you, I had a spouse who would not admit this was becoming a major problem, and I was on my way out the door when my Mom suggested Al-Anon. I was so angry that day! I marched in and sat down and asked this group when it was my turn to speak said something to the effect of "what the heck am I suppossed to do to get this guy to quit drinking so damn much?" I got a lot of smiles and sympathetic looks, and afterwards a group of ladies sat me down and told me the purpose of Al-Anon. I didn't go back for another month. I thought I was going to get good suggestions on how to fix him! ; )
I read all the literature plus more books, and went back that second month with a different attitude. I tried a variety of meetings and met a lot of really cool people who just seemed calm and peaceful...and I realized I wasn't and wanted what they have, living in the midst of some major stuff, to be so calm and peaceful. So I kept going back. Some days were better than others. But I can honestly say I learn something at every meeting.
When my stbx-RAH found out he BLEW sky high. I didn't tell him at first and didn't feel the need to, as this was my business and as an autonomous person even being married, I have a right to make my own choices. Anyway - it was ugly, but because of what I was learning it didn't last long. But he was very threatened by it, and heck, probably still is.
You do this for you, because your life has become unmanageable living with an active alcoholic, not because you think it will prove anything to her or force her to look at her own stuff. Do ti for you, and you will get good things out of it. And try meetings until you find a good fit. You'll know it when you find it.
Congrats on an important first step of taking back your life.