One of the things I did while I was trying to decide among my options was watch a robotic prostatectomy on YouTube*. When the surgeon cut the seminal vesicle loose from its connection there was a squirt of milky goo and I remember thinking sadly that the patient has slept through his last party. Don't let that happen to you.
I am pretty sure that sex a few hours before RP makes absolutely no difference whatsoever in the surgery or its outcome. If anything it will save the surgeon the one or two seconds it takes to suction things away.
Tell your anesthesiologist about your Xanex. He will tell you "Yes, most guys do; we've got it covered." so nothing to worry about there.
You seem to have missed the most common before-surgery question, ie. why me?'
You'll do fine.
*I don't necessarily recommend watching the operation on the Internet, especially for nervous types. But, to assuage your curiousity, it looks like an ultra-closeup of a guy poking around in a bag of raw chicken livers with a pair of Swiss-army-knife pliers and a soldering iron.
Peter, one of the surgeons I met with, took us through a power point and a video of the surgery. My wife was looking at her shoes the whole time, doing math problems in her head to distract herself. It was hilarious.
As far as why me, that would be typical of me, but for some reason I never asked that question. This happens to too many men. I'm not that special. It is what it is