Andy, best of luck with your mom, however it goes. That's really scary, that's the whole reason I'm not 100% out to everyone, I still technically live with my parents (I spend 2 nights out of a week there and it's my legal address but I hardly "live" there, it's complicated) and I'm worried my dad would flip out and either kick me out permanently or make my life a living hell.
Personally, I'm only scared of two things about surgery: Complications, and effin needles.
My biggest fear is that I'll die, honestly. I'm really, really paranoid about nearly everything so I think of surgery and all I can possibly think of is everything that could imaginably go wrong. Which, admittedly, only makes it harder.