congrats Hayley!
I had an emergency C with my first and they put the catheter in before general but on the op table I remember it did feel uncomfortable, not painful but you knew something was happening. Then again I was in labour and didn't care what they did
Second time around I had an elective and a spinal block on the table and the catheter was put in after, infact until you mentioned it I hadn't even thought about when they put it in, I didn't feel a thing and they're down that end anyway. I think they have to massage your placenta manually and I'm not sure if that comes out your woohoo or the incission?? either way they put a pad on you post op and clean you up but you just are so overwhelmed and preoccupied you don't notice.
Coming out a nurse does it in your room and it didn't hurt for me although it does feel a bit weird when you have your first wee but nothing major and it goes back to normal very quick.

GOOD LUCK!