Thank you everyone for the advice. How am I going to feel after the surgery
Please don't be worried if after surgery you feel like you've been run over by a bus. I've had similar experiences to highlandsrock - a couple of days after the surgery, the anaesthetic wears off and the pain can increase at that point. I think it's worth being mentally prepared - you will have pain, and you'll have a general feeling of malaise and nausea from the anaesthetic. But you will also see that, if all goes to plan, you'll quickly start feeling better.
Medication can really make a difference to the earliest, hardest stage of recovery - getting on the right pain meds, anti nausea meds and something to help you sleep will make this period go much more smoothly. Tell the nurses if you're in pain, if you feel sick or if you can't sleep (all of which usually happen for at least a few days/nights after surgery) as they will usually have instructions from your doctors about extra meds you can take if you're feeling bad. The nights will be worse than the days.
You probably won't want to eat at all at first. If you're trying to gain weight, don't panic at this. You should get your appetite back pretty quickly. If you can't face eating, drink a lot of high-calorie drinks to keep your weight up - you might find this easier than eating a lot of solid food.
In my experience recovery should be linear - day by day you should feel noticeably better. If at any point you feel like you're not improving, let a doctor know right away.
Once you get discharged from hospital, you'll be so glad to be home where it's comfortable and have your own bed and your own food, you will probably find you feel a lot better.
You will start to feel like a human being again. Maybe after a few weeks or so. After that, you'll suddenly find you've resumed normal life again, hopefully feeling a lot better than before the surgery.