I think the best advice is to go into surgery with a very clean and empty colon! I've heard that not all transplant centers insist on a bowel prep, so if yours does not, consider just prepping on your own.
Get up out of bed as soon as they will let you and start walking. Depending on the time of day of your surgery, they could have you up out of bed the day of surgery, or, at the very least, the next morning. Don't over do it, but do as much as seems reasonable. Walking gets everything working again.
If you can, avoid the narcotics after you leave the hospital and stick with extra strength tylenol. It doesn't mess with your head or GI tract, but takes the edge off the pain.
Stay well hydrated!
Our hospital was very busy the day of our surgery and there was a bed shortage, so we were in the Post Anesthesia Care Unit way too long...my brother got out at 9pm and I was there until midnight. That was the worst part of the experience for me because at that point, I wanted a quiet, dark room to sleep in. I wished I had a sleep mask and my noise reduction head phones. When I got out of the hospital, I sent my headphones to my brother, and they made a difference in the ICU experience because he could at least block out a lot of the noise.
Everyone on this site has been more than helpful.
Giving my brother a new lease on life has been a very meaningful experience. Best of luck to you!