Just to let you know that your fear is common! I was TERRIFIED of dying on the table. The last thing I said to my surgeon was, "Don't kill me!" and he said, "You're not going to die. Don't worry."
I was sleeved 16 days ago and so far I have been lucky and had a dream run. The first 6 hours after surgery I was in a lot of pain (although I have say I was sleeping for some of that time - but it took about 6 hours to get the right combination of drugs to keep me comfortable.) Other than that I really haven't had many problems. I had existing issues to content with - adhesions from previous surgery and a hiatus hernia, but everything still went fine.
I am so happy I made this decision and that I went through with it.
Good luck for your surgery. May will be here before you know it!