I wish you the best of luck w/ your surgery. Two weeks ago I had a colon resection (sigmoid, rectum and anus removal) but it was open like what you're scheduled to experience. I've also had a small intestine resection about ten years ago, laparoscopically, so I can empathize w/ you on both sides. But the open surgery is fresh in my mind if you have any direct questions you'd like to ask.
Obviously, surgery is no picnic but I would have advice for you that you're free to take or leave. I was in a lot of pain the day of and after surgery and the nurses or phyisical therapists or doctors (lots of pain meds, couldn't remember who) INSISTED that i WALK the day after surgery and it was just too painful. One nurse mentioned, sorta off the record, that it'd be just okay if i were able to sit up and sit on the edge of the bed rather than try to walk. So i refused the walking until two days after surgery and tried sitting on the edge of bed for a few minutes until i could bring myself to walking.
I hope your surgery goes well and don't let fretting about it get to you. You're going to feel night-and-day better /after/ wards and going to be so glad you got resected. Feel free to message me if you have any questions about my experience you'd like to hear.