I was horribly nervous when I took my first lady in to get a tumor removed. I kept putting it off because I just knew the outcome would be horrible. The vet I take my ratties to lets me wait for him to finish and I get to take my rattie home that day. That helped ease my mind tons, not to mention he was done very quickly. I was VERY pleased with how the surgery went

. The hardest thing for me was actually getting enough nerve to take my lady in to get it done. Once it was over it was like a ton of bricks were off my back. I've now had at least 7 tumors removed from ratties and they're all fine. Actually all were pretty much back to normal later that day, but one and she was a little lethargic for the rest of the day, but the next day she was back to normal. So I know how you feel.
Best wishes to you and your lady.