Ditto for what the the last poster said about the ease of the procedure. I've had 7 of them done over the years and don't even feel anxiety any more when they're scheduled. Some people do have some troubles though, but many are just fine.
The only serious complications of the procedure (and this happens in less than 1% of people undergoing the test) is allergic reaction to the anesthesia or puncturing the esophagus or stomach lining during the procedure, but once again, THIS IS RARE! Do not cancel the test just because of potential side effects - your GI issues will not go away by avoiding test procedures.
Your doctor has been in practice many years, but find out how many actual endos she has done - the more the better. After that much time in practice, she should have performed several hundreds of them and be proficient. But if you have any doubts find someone you trust. I trust my GI doc completely (he's actually a general surgeon, but does many endos & colonoscopies weekly), which really eases any fear I might have.
Good luck to you and keep us posted on how things go,