I'm cishet. I have no possible way of fully appreciating what you're experiencing.

That being said...

Trusting your gut is entirely valid. It's not 'chickening out' it's just that, for whatever reason, you were not 100% committed. That's OK. You just were not ready right then and there.

Don't worry about the surgeon, they'll be much happier knowing they didn't operate on someone who changed their mind (per se) once it was too late.

Be strong, be well.