Suzy,
It's so so hard to go in to these kinds of surgeries, because they are totally optional. And we know how big a decision this has been for you. The day or two before a surgery ... these are the days that are so excruciating. I'm so relieved to hear they will keep you overnight though so they can monitor pain levels and just generally take care of you.
We're all here for you, and looking forward to a recovery period that goes as smoothly as possible, and most especially for the time really soon when you can look back and be so glad to be healed and feeling better.
(If your anxiety gets bad in the next day or so, maybe your doctor could write you a prescription for some Valium to start on a little early.)