A lot of surgeons don't bother with any bowel prep before bowel resection surgery. Some use only an enema on the morning of the surgery.
You can ask to use whatever prep you find the most suitable (but I wouldn't worry too much about
how much you manage to get down.)
You will fast from midnight the night before. If you generally feel back up, eat lightly a day or so prior.
The main thing is to be as healthy and peaceful as you can be
Take care and relax in other words (easier said than done.)
Wish you all the best.