Lot of educational stuff online about bariatric surgeries, YouTube has some great videos describing the surgeries step by step. Maybe you can watch one together or perhaps take him with you to next doctor visit and he can ask questions to the surgeon and staff
As for the Endoscopy the hospital should be prepare for all possible situations. most are i am assuming. Ask the questions who , what , where and how until you're comfortable with the procedure. By even concerning the surgery you have taken some control of your life, don't stop now. ask questions ....good luck
"you got this "