Don't worry. Your baby will do just fine in surgery and recovery.
Ralphie, who's 5 yrs old, had bladder stone/crystal surgery about 2 months ago, plus they cleaned his teeth and neutered him. I was more worried about the anesthesia than the surgery. He came home the same day and was very groggy for 2 days. By Day 3 he was feeling better but he was obviously in pain because when he went to bark at the UPS and Fedex man at the door, he cried out in pain but he tried to be feisty. He healed fine.
As far as diet, they doctor put him on Hill's Science Diet Prescription U/D. I find him gaining weight now and I'm very concerned about the food. He is on medication now for a month for a staph infection, Lord knows, I hope it wasn't from the operation, and I'm wondering if that's contributing to the weight gain.
I remember the vet said he could continue eating his Life's Abundance food if I wanted but he would have to stay on medication for the rest of his life if I went that route. I decided to switch his food. I'm not fond of permanent medication. He also said there is no guarantee that the stones won't form again but by keeping him on the special prescription diet, he has a much less chance of it recurring.
Follow your vet's advice and you'll all be fine.