I think "they" say that a slice or two of bread, or a good serving of crackers a day would be sufficient.
I know it's crazy to keep yourself sick in order to get answers, but unfortunately that's what it takes!
If you have the will to keep to a gluten free diet for life, you could accept the doctor's diagnosis from blood work (a lot of docs won't diagnose on blood work alone!) and skip the endoscopy.
You'll get mixed answers if you ask whether you should do the scope or not, some will say "yes" some will say "why bother". In part, a positive scope can solidify your determination to be disciplined about gluten consumption...I would get a copy of my blood tests and see exactly what they tested. If they did a full panel, and several tests were positive, that is a pretty strong indication that the celiac diagnosis is correct.