KittyLady,

Don't worry.
I've had it done that way and it was very much OK. Just keep swallowing if you start to gag and the tube will go down more easily (even if you tend to have swallowing/choking issues).
I've also had it done under a light general, which was way better...but you don't get to see the cool images on the screen with that method. It was the best sleep I've had in months though .

Hope that all goes well and easily for you.
In my thoughts and prayers .

With love, Erika