I haven't had surgery for Crohn's, but I've had several surgeries including rectal sugery, so can give you general ideas.
Surgery is often laproscopic now, which greatly cuts down recovery time. I was only in hospital 48 hours after my most major surgery, and have tiny tiny scars. The aneasthetics are supposedly improving all the time too - though you may feel pretty rough, depending on how long you're out for. They usually want to get you home as soon as possible, which I imagine is what you'll be hoping for too.
I didn't have to prep but was given an enema before my rectal surgeries. I just had to not eat or drink on the morning of surgery.
When I've had minor surgeries, it just felt like having a mild flu for a day or so after. Major surgeries, it's like a bad flu for a few weeks and some pain from the incision. Do you know what type you'll be having exactly and roughly how long they expect it to take? That will give you a good idea of recovery time.
You'll probably be on a special soft diet afterwards. You'll get to speak to the surgeon and aneasthetist beforehand, so come up with a list of any questions you have in advance.
When you're recovering, remember you can always call the nurse and ask for more pain relief! And things to help you sleep or help with things like nausea too. Make sure you don't suffer unenessarily. One time I was feeling so sick for ages, just from the anaesthesia, and when I eventually told a nurse she gave me a med that took the nausea away like magic. They seem to have things in hospitals that aren't so readily prescribed for long-term use at home, so when you're in this situation, make the most of it, if you want to.
Then when you're home, keep your doctors updated on any potential problems. I don't know what country you're in, so it may be different, but here I was able to ring the hospital and check in with my surgeon. They should tell you how to look for signs of infection (unlikely to happen unless you are predisposed somehow), and will probably make you a couple of regular appointments to check you're healing well or change dressings.
Do you have any specific questions? As I said, my surgeries haven't been for Crohn's, but I have had quite a few. I'd imagine that each surgery's a bit different anyway, even for resections.
Good luck, when you get to it, it's not so scary!
