I have neutered all of my male dogs and it´s a simple "in and out" procedure that´s not as half as hard on them as you´d think
Mine have always come home just an hour after having it done and although they do act sluggish for a little while (like a few hours) they tend to bounce back
very quickly, and you´ll find you have to hide toys etc to keep them still
The first time, I expected a few days of whimpering and my boy feeling
very sorry for himself, but nope..within a few hours of the operation, he wanted to play with his ball and he was bouncing about and pawing away at his "lamp shade" because he hated it lol
You might want to feed him a light meal the night he has it done, because the anesthesia can make them feel a little sick for a while afterwards.I fed mine some chicken and rice in small portions just in case, but they were fine.
Try not to worry (not easy, I cried when I handed mine over to be neutered lol) he´ll be totally fine