Neutering is a much easier procedure than spaying. It is less invasive, that is why neuters get to go home the same day and spays have to stay overnight. Where I work, there are no stitches so you don't have to come back. My 2 male cats were fine by the time I picked them up. Just a little sleepy. I did not have to separate them from the others, but if you feel more secure in doing that, you can. My other cats did not try to go for the spot, and neither did the cat who got neutered. He should have no trouble going to the bathroom and you do not have to switch foods. Healing time is relatively short for neuters. My cats became a little lazy after they were fixed. However, they did not gain any weight, although some cats do.
hope this info helped!!