I got real tired of green or yellow Jello and chicken broth the day before. I had family come into town to sit through surgery, and had to cook for them. It was a long day.
There was no magnesium citrate in my plan.
The doc will also load you up with post-op instructions and prescriptions - be sure you (or someone with you) understands them, knows where your pharmacy is, and has your insurance card & ID. I had to give directions on the way home to the folks driving, who were from out of town, while in 10+ of 10 pain in the car, then have them go to a pharamcist who knew me, but not them, asking for seriously controlled pain meds on my account. Nothing good comes of any of that, trust me.
The nurses should go over catheter care - that is important as well.
All that said, the one who has the easiest time of it, and who will get the best night's sleep after, will be you. I didn't sleep more than two hours any night from the time I was diagnosed until surgery day. But that night after getting to the room, I remember nothing. Pain meds knock me out, and they worked like a charm.