You won't even remember it. I've gone through two, and they did not bother me at all.
The anesthesia used in both of my cases was the type where you are "asleep" but you are really awake and can respond to commands. You don't remember any of it, so to me, I was asleep. It was very easy and they made it very comfortable for me. I went into the office, they put me on a bed, did the normal check blood pressure and all of that, then ran an IV into my arm. They wheeled me into the room and that's the last thing I remember. I don't remember them putting in the scope, or anything. An instant after I faded away I woke up in the recovery area. about 30 minutes later I was able to go home. I was very tired and couldn't drive, but there was no pain or discomfort at any time through the process. Never gagged since I wasn't awake. The procedure takes usually 10-20 minutes and you are out a little bit longer than that. Its very short. You'll be able to eat and basically do anything right after. (don't drive, you'll be very tired the rest of the day, you'll probably sleep a lot)
After my second one, apparently I had a full conversation with my doctor and my dad who had driven me there, but I don't remember any of it. Ha!
Your doctor will probably take biopsies, they commonly do. I got the results from both of mine about 2 weeks after the procedure.
Good luck, I promise that you will wake up after going... "I was scared over that??? It was nothing!"
Nissen Fundoplication - 11/22/11