I spent a fair amount of time in group counseling about ten years ago. This was for substance abuse recovery, not specifically SA, but I believe the principle is pretty much the same. Once I adjusted to the atmosphere, I found it remarkably comfortable and supportive. I was pleasantly surprised by the sense of camaraderie that can quickly develop within a group of complete strangers once they discover that they're all in the same boat.
I started out just listening to other people talk about their issues and problems, but pretty soon I was putting in my own two cents, making suggestions, offering support. One day, it just seemed natural to start talking about my own issues, and in the following weeks, I received a lot of help in dealing with some of the stuff that was troubling me. I won't claim that it was easy or that it solved all my problems—it certainly didn't "cure" me—but it did help a great deal, and I doubt I'd still be sober today had I not done it.
SA, of course, changes the game considerably, but if you're going to a group that specifically addresses that condition, you'll find that everyone else there feels a lot like you do. They'll have had many experiences similar to your own—the kinds of experiences that seem ubiquitous among people like us. Once you get past the initial fear, I suspect you'll find it just as comfortable and rewarding as I did. I certainly hope so.