You are doing the right thing, buddy! it took me three years to spay Minnie. Her sister was spayed much earlier but the recovery was very stressful for me (and for her) so it took me the long while to decide to spay Minnie, even knowing the risks.
I am a veterinary nurse by trade, so I will base my info on the way my clinic used to work with bunnies for spaying. I spayed Minnie there as well. Mira was spayed somewhere else and I really wish I didn't do it back then - the vet had no rabbit knowledge. :evil: What you should be prepared for is that if vet thinks they should stay for the night, the vet has good reasons for it and you should not object, as stressful as it feels. but most often bunnies are sent home when they are fully awake and eaten. If the rabbit did not eat the vettech will make sure it was force-fed, to get its digestion going. Bunnies get painkiller treatment prior to operation and that lasts 24 hours. the good vet will give you painkillers to go as well and a syringe to administer it orally. If the rabbit is not all that enthousiastic about eating, you might get a intestinal stimulant called Cisaral, it makes bunny intestines move and thus produce droppings. I would ask if they have any Critical Care you can have - handy to have around and you will need it dearly if bunny does not want to eat.
At first you can layer the bottom of the cage with a towel, just to be sure that no hay will poke in the wound (tho usually it is no trouble), first three days are the days where the pain is the worst. Usually it takes 3-5 days for animals to recover enough to go back to their usual tasks. A week or week and a half of relative cage-rest is needed. You might see lessened mobility, hear loud tooth-grinding and the rabbit will look a bit miserable overall. I made sure the hay, the water and the food all all within head stretch so that Minnie did not have to move too much. If you stroke them and they feel cold - fill the water bottles with hot water, roll them in a towel and place it near (or between) the buns. Never place warm source without a towel, it might cause burns! They have to start pooping within 24 hours. if you did not get Cisaral - contact the vet. if you did - it will come. It was somewherre in the evening the next day when Minnie made a ginormous smell pile and I was extrememly happy. Give them all the food they eat. Especially their favourite things, they need to eat something. Minnie, for example, really likes parsley. So I kept giving her some parsley twigs at first and then she passed onto her pellets and hay.
I think I, sort of, covered all bases. The most important is to call your vet the second you think something is not quite adding up. if it is a bunny-savvy vet, he or she will understand the nessesity of this. I had multiple clients calling repeatedly with questions about 'why she does this? And that?' Better ask then not.
Good luck! ^^