His surgery will be just fine sweetie!!!
I'm a vet tech- thursdays are spay/neuter days at our shelter. Male kitties by far have it the easiest as far as the surgery goes
They are going to sedate him with a shot to knock him out, shave him (just in that little area), disinfect the area, put him on the table, put iodine on the site, then make the incision and fix him. Neuters on male kitties are usually very quick and easy
No worries gorgeous! Also- ask for them to give him a shot to reverse the anestesias effects after his neuter. (Kitties are sensitive to anestesia- so it normally takes them a while to wake up afterwards if they don't get a shot to reverse the anestesia. kittens take longer in most instances than adult kitties. Sometimes there is no need to give an adult kitty stuff to reverse it, but you might go ahead and ask if you're wanting to pick him up at a set time and have him be coherant.) This is why most spay/neuter appointments are made in the morning for kitties- so that they have plenty of time to wake up and be ready to go home at night/afternoon when their owners arrive. You can also ask for some Metacam for pain as well but he will probably not need it. There should be no stitches to worry about having removed as the skin will probably be folded over and all so you shouldn't have to mess with that. Also- he may be a little grogy when you get him home- be sure to just give him water for the first few hours and then when he's up and moving, give a LITTLE bit of food -not too much because the affects of the anestesia might make him a little nausious. If your kitty isn't already microchipped and you are interested in having him chipped- please have them do it right before the surgery tomorrow when he's sedated (same for vaccines if he needs them) so he will be asleep while it's done and won't get stressed. Good luck! He's going to be just fine!
Also- use some shredded newspaper in his litter pan for the first few days he's home instead of litter to avoid and dust/particles getting into the incision site and causing an infection. (rare in male kitties- but just as a precaution).