Don't be scared! I had one a few years ago. It's really not that bad at all, you're under a general and nothing hurts at all. I didn't even have a sore throat from it, the worst thing I experienced was feeling so groggy for the rest of the day from the general.
I was a little scared, it was my first general (I was 16) and I didn't know what to expect; I went in, had the canula put in that they put the anaesthetic through, counted down from 10 - I think I made it to about 6 lol - and the next thing I knew I was waking up in the recovery room. No pain afterwards at all. I'd been told that some people can have a bit of a sore throat for a little while afterwards, but there's really nothing that can go wrong. It's a disgnostic procedure, and a very common one - the doctor has probably done too many of them to count!
Don't worry, it will be fine smile