There are "newcomer" meetings, yes. They'll be marked as newcomer, usually they're before a regular discussion/sharing meeting. It's 30 minutes, and the person who is leading will explain the 8 tools and answer questions. People will start to trickle in (if there's a meeting afterward) and everyone is really nice, really welcoming.
My newcomer's meeting was a bit awkward (nobody made me feel awkward in any way, it was my own defenses springing up), I felt like everyone was going to know why I was there. Well, DUH! Of course they did! and they were there to welcome me, and to help me. They also gave me a newcomer's packet, which is some pamplets and writings that explain more about OA and help you determine if OA is right for you.
They say you should go to 6-7 meetings before you make a decision. For me, I knew in my gut that it was right for me from that first newcomer's meeting. At my second meeting (the monday noon after my saturday 8am newcomer's) I met the woman who is my sponsor, and the next day I was abstinent. And it's been incredible, really. The network and support of OA is intense, and it's something you won't get from a therapist. No offense to therapists, they just can't be there all the time, and you're lucky if you get about an hour a week. OA is REALLY structured to help you. I encourage you to give it a chance.