I had two a couple of months ago.
Yes the prep is the worst bit. I actually couldn't get the stuff down, I was crying and it had a nasty aftertaste so all the advice about take a sip of prep then a sip of orange squash didn't work.
Because of the lack of prep they could only see about half my intestine due to poo still being there, they did note 2 polyps.
So I need a second one to remove the polyps, for this I did prep over a week. You live on a 'low residue' diet, things like white bread, and non of the things you are normally told are healthy. I took senna every night.
I had to do a final prep on the morning of the colonoscopy and I threw half of it up. I chilled it this time as others on here had recommended it.
Anyway the second one was fine, they removed the polyps and tattooed me.
When you get to the hospital you will put on a gown and some 'modesty pants' these are like huge bloomers with a slit at the back.
When they put the scope in I felt a cold 'push' no worse than the when a Dr performs an internal.
I had sedation but I also became fascinated looking at the screen.
They do have you move around a bit, onto your side, on to your back etc.
I took tea and biscuits for the department, but that's just me.