My little lady had a tumor removed this morning, I was nervous too, but everything went just fine, and the vet called me as soon as Crass woke up from anesthesia. I know it's scary having your little one get cut open, but if the vet knows what they're doing then there's not much to worry about. There's always a risk with surgery, but if you have a good vet then it's pretty small, and far better that the alternative.
This was my first time having a rat get surgery, so others on here might be able to tell you more, but so far Crass has been a bit slow and clumsy, and seems to just want to rest (aside from emptying an entire box of tissues). I put an extra water bottle and food dish in her cage, so she doesn't have to go to far to eat and drink.
I know how you're feeling, just try to keep busy and stay calm. :hugs: