Hmm off the top of my head...send him in with a little box of his normal food so he'll have something to eat when he wakes up (often the vets won't discharge them till they've eaten)
If he normally lives outdoors, it would be better to bring him inside for a little bit so you can keep a close eye on him. Ideally have him in a cage or pen lined with pale towels/sheets so you can easily spot if there's any bleeding. When you pick him up from the vets, have a look at his wound, so you know what it *should* look like, and check it twice daily once he's home in case he pulls his stiches.
Make sure they give you some pain relief for him. Imagine how you'd feel if you'd had your whatsits chopped off - you'd definitely want some painkillers, rabbits are just the same!
If he's not eating/pooing afterwards, phone the vet straight away.
Good luck
I hope he does well. They are both adorable.