OK, I had my teeth taken out about 7 months ago, so let me tell you how it worked:

I went into the room about... 8 15 AM. I requested gas to knock me out, so that's what I got. They hooked me up to a mask, and the gas started. I immediately started giggling, the doctor said something smart about how I shouldn't be laughing yet, and I felt my eyes slide upwards and close.

The next thing I know, I'm half-awake and a bit hazey, sitting somewhat-upright in a different room. The clock says about 9:30. There is a CRAPLOAD of guaze in my mouth. An IV is in my hand, I can't feel it, but it runs out and starts pulling up a bit of blood, in my stupor I (not really) frantically tell the nurse to take it out.

Anyways, long story short, eating that day and the next was a bitch, it didn't actually hurt horribly but it was really sore, the operation itself was a piece of cake (Since I wasn't awake for it)

Trust me, mine were coming in, it'll hurt 10x worse if you leave them in. Get them out. All at once.