What to expect after bone grafting for top of mouth?

The bone in the top of my mouth has deteriorated and the specialist needs to do a bone grafting where he pulls out all my top teeth and rebuilds the bone. Then I'll have a retainer-like plate on the top of my mouth that he said will feeling like I'm gagging and there is going to be lots of swelling. I'm a nervous wreck. Has anyone had this done? What can I expect? Will there be a lot of pain and for how long?