How will the hospital put me to sleep for an eye operation? Scared?

I should be getting a eye operation some time this year hopefully, which involves skin cut away from my upper eye lids and pulled back so my eyes appear more open. I'm 17, and I'm really scared! I've never had an op before like that in my whole life. What will the doctors do to put me to sleep? Injection, gas, something else? Also what if I waken up during the operation? I am SO scared about that. What is it like after it? Any info about it would be great, thanks.