It took 2 weeks after neutering for my Bam to stop displaying sexually driven behavior. In some buns it may take up to 8 weeks, but I think 2 weeks is the most common.
Tomorrow you should feed him right before surgery, bunnies should not fast like people or other animals. When you bring him home you should offer him a selection of his favorite foods, it’s very important that he starts eating asap. If 12 hours go by and he’s still not eating, you should syringe feed him pellet slur or Critical Care. If that happens, post again for more info. Give him water in an open bowl, a bottle may be too bothersome when he’s not feeling right. See to it that he keeps warm, a hot water bottle with a towel around places so that he can move away from it is good if it’s chilly. Bunnies can get hypothermia in connection with anesthesia. Check for poop. Poop is good and means the tummy is working.
Other than that, check the incisions twice a day for redness, swollenness or leaking fluids. Most bunnies recover very quickly, but they should not be allowed to jump or climb for about 48-72 hs post surgery.
Good luck!