I know how you feel.I get worry every time I have to take one in for any type of surgery. I've had pets my whole life, all of which were either spayed or neutered. I'm batting 100, I would say those are pretty good odds your boy will be okay but still you can't help be a little apprehensive.
I just had my Duchess spayed in June and her little butt was at the vet's playing when I went to pick her up
I was expecting for her to be all groggy but she was wide awake, alert and wagging her tail. She didn't seem like she was any pain but I gave her some pain meds before bed time just to make sure.
By the next day, other than her incision, there was no way of telling that she had surgery the day before. She didn't seem sore or sluggish at all. I actually started wondering if she really had surgery. It was tough keeping this ball of energy calm. I had to put her in expen which of course she hated.