"Will I choke or stop breathing?"
No. The scope goes down the food pipe, not the windpipe, and you breathe normally. Your oxygen and pulse are monitored throughout.
"Will it hurt?"
A throat spray numbs the gag reflex, and light sedation makes most people comfortable and drowsy. You might feel pressure or bloating. An upper endoscopy takes about 5–10 minutes.
"Sedation or not?"
Light sedation is very safe in healthy people with monitoring. You can choose no sedation for an upper endoscopy, but it's less comfortable. After sedation you'll need someone to take you home.
"What if I say something embarrassing?"
Most people simply sleep. Staff have seen it all, and it stays in the room.
"They took a biopsy. Is it cancer?"
Biopsies are routine, to check for H. pylori, coeliac disease or inflammation, or to confirm something is harmless. Most are normal.
"Colonoscopy prep is horrible."
It's the hardest part for most people. Split dosing, chilled solution and a low-fibre diet beforehand make it much easier. See preparing for your procedure.