Amore,
I'm petrified of anything like that, and totally understand where you're coming from. I've not had any surgery to help transition, but I have had emergency surgery. I made sure that they knew of my allergies, and the sheer terror that I had - I had no option, it was do or die.
They provided some sedatives to help calm me (still wasn't enough, but, better than none), and the anaesthetist changed the whole drug order when she knew of my issues.
As a result, when I came round, I was ok, and the pain meds were given very regularly and kept on top of it. Don't be a martyr, and try to do without, you'll feel much more like yourself if you can keep the pain at bay by proper use of the meds.
Anxiety is to be expected I think, but I think you've got this and I know you can do it

Rowan