For oral surgery you are generally put under general anesthesia - this means that you will be "asleep during the procedure" You will be given an IV, probably in the arm, with Versed or another sedative drug. After you are "asleep" you will then be given local injections (shots) to numb your teeth. You will not feel these injections. When the procedure is complete, the oral surgeon will stop your IV and you will wake up. You won't remember anything about the procedure and will probably feel pretty groggy. As a side note, "laughing gas" doesn't put you to sleep, it just relaxes the person receiving - you are still awake, completely concious and can feel pain, etc. This is why general anesthesia is used, and not gas, during oral surgery procedures.
Don't worry - general anesthesia is the way to go - pain free! Your oral surgeon will give you plenty of instructions/information so you will be well informed.