I'm using an 11" Momo. I know I paid over $100.00 a few years ago. The hub adapter at that time was $75.00. I think they're around $94.00 now. I also use a 13" deep dish no name from ebay. I paid around $20.00 for that one.
First, I disconnected the battery for safety reasons. I didn't want any power going to the bag. After loosening the screws, just pry off the airbag cover. Screws will stay on the steering wheel. In my picks, I outlined where you need to pry off.