Congratulations! I am so excited for you. The endoscopy will be something you can get through pretty easy. My friend had one before her surgery and the only thing she noticed was a bit of a sore throat. I don't know about the IVC. I haven't heard of someone needing that done. Onward to a better you!
I have Kaiser Permanente and it was approved first time around. They did have a year of data with nutrition, psyc, sleep study, blood tests, classes, etc.