As you know I have had loads of GAs but always on the water works so can't directly answer the retention question. I can't see why the op and GA should affect the waterworks.
The obvious way into the bladder apart from the urethral route is a suprapubic through the abdominal wall. My first one was in the recovery room and although not my favourite pastime it was tolerable, bear in mind I was just coming round from the GA, it probably helped that I was a bit groggy and the morphine helped. The suprapubic hole seals itself within minutes once removed.
The other option is self catheterization, you can get some very thin catheters, could you try some pre op ?
I have also had a full dilatation and catheterization without any pain relief at all, again not pleasant but tolerable.
I do understand your concerns, but is the nose op going to improve your quality of life.
Take care thanks Chris