You sound like I did 8 weeks ago. There is no such thing as a good nights sleep, but believe me, there is nothing to worry about. I wouldn't even listen to my own advice had I not had the surgery!
You'll wake up all nervous, wanting to cancel (well I did!), but I thought thought, I've come this far and the people here on the boards have helped me so much. Once you arrive at the hospital, gone through the paper work, you'll be wheeled in (I was laughing and crying at this point!), you'll have a nurse with you to keep you company and then before you know it you'll be asleep. Next you wake up and it's over, you'll be then concentrating on your recovery.
So, good luck and try not to worry and I look forward to hearing how you got on when you return home