Don't worry, neutering is not a big operation. Generally, rabbits recover from it almost immediately. I've had several bucks done, and they were all eating and behaving normally 2 or 3 hours after being back home (it's not like a spay, which leaves females hurting and feeling off for days). The main things for me are pain management (as stated in the article - it's a light surgery, but it still hurt a bit, so metacam it is... ^^) and offering tons of good food (lots of hay ; the rabbit favorite vegetables ; things like mint, parsley or basil... - wet greens are always good to hydrate the guts and get fibers, and they are more enticing than hay for most rabbits) to make sure the guts are working again as soon as possible.
Beside that, just put the usual routine back on track immediately, act normal and leave the rabbit alone so he can relax and understand that this whole scary thing at the vet was a one off.
Honestly, I was always really impressed by how quickly rabbits bounce back from this. When I got my first boy neutered, I remember crying when I left him at the vet and feeling awful about the whole thing. But when I came to take him back, the vet telling me that after the operation, he just woke up in his cage and started eating his hay like nothing happened. Indeed, he didn't like the journey back much, but he was just super chuffed to have tons of food when we came home ^^.