If you take painkillers before you go (assuming end up having to go), do NOT take ibuprofen or asprin. They will thin your blood and you will bleed a whole lot more than you normally would and your blood won't clot as well. Acetaminophen might not be as bad, but I wouldn't take anything because who knows what it'll do when combined with the anesthetic.

If you can get put under for your surgery, it really isn't that bad. The anesthetic knocks you out pretty fast. Yeah, you wake up later with a mouth full of bloody gauze, but trust me, it's way better than having to go through the surgery conscious or even semi-conscious. When I was younger I had to get teeth pulled before I got braces to make room, and they put me out for the surgery. It was a synch. When I later got my wisdom teeth out they refused to put me under because I had a history of sleep apnea while under anesthetic. So I was only partly anesthetised... and it SUCKED BALLS being even semi-conscious during that shit. Trust me, you want to be asleep.

Anyway, talk to your dentist. They'll be able to tell you whether or not you have enough room. And like Bob said, the pain during recovery is much more bareable than if you leave them in and don't have room for 'em.