Prep is horrid, procedure itself is a piece of cake.
Be sure and do all the prep, since if its not completely cleaned out, they sometimes can't perform it all.
Are you getting IV sedation? It's usually a twilight sleep, only lasts about 45 minutes or so. I woke up during my last one, because it took them so long (LOTS of biopsies and such to do). Even with waking up, it's not a big deal.
I have a friend that does hers without sedation and she makes it through =)
When you're done, you'll likely go home and crash - oh, and eat on the way home since you'll be starving! I never remember what I do during this period between waking from the hospital and leaving and waking up after my nap at home later. It's so funny =) DH swears I act coherant!
Good luck! Bring your laptop to the bathroom, or some mags, or something. I hooked up a small tv one time in the bathroom...