Hi!
Most of us here have had rabbits neutered. It’s not a big procedure for a boy, but there are a few things to keep in mind:
Don’t fast him before surgery. Rabbits can’t vomit, so they won’t vomit during anesthesia.
Have a hot water bottle, plastic hand warmers (the type you “break”) or a snuggle-safe in case he need extra warming up when he comes home. Rabbits can get hypothermic after anesthesia. He must be able to move away from the heat-source if she doesn’t want it. Don’t use an electric heating-pad because rabbits live chewing cords.
Serve him water in a bowl when he comes home, he might not want to bother with a bottle.
Get his favorite leafy greens so you can entice him to start eating asap. Fragrant herbs are often popular. It’s good to have some Critical Care in case he needs support-feeding, but most male rabbits will eat on their own.
Many safe-neuter-vibes for (((((your bunny)))))

Yes definitely offer him a water bowl. My bunnies snubbed bowls completely til after their surgeries. Now they won’t touch a bottle.

My little girl bun was a bit cold when we bought her home but she wasn’t interested in a heat pad (typical!) so we put her hutch near the radiator and turned the heat up a bit. It was warm but not overly hot. She warmed up nicely

My boy bun had a pretty good appetite, he started munching hay 10 minutes after waking up from the anaesthetic! But back home he filled up on romaine lettuce, sunflower petals, dandelion. Basically, all his favourites! Definitely have your boy’s favourites on hand, as it’s important that he eats something. If he doesn’t seem to want to drink, you could give his veggies really wet so he gets some hydration. Keep an eye on him to make sure he’s peeing and pooping but don’t be alarmed if his poos are a little odd. They will take a little while but they should go back to normal.

Good luck with everything! I got great advice here when I made a similar thread prior to my bunny’s surgeries