I'm very familiar with colonoscopy as I had it done in May. Several friends have recently had the procedure as well, primarily because we are about 50 and docs recommended it.
I had some complaints as well, so they were checking me for colitis, too.
Long story short: the preparation is nasty, but certainly not intolerable. You just have to spend much time in the bathroom but there is no pain involved -- you can drink the stuff they prescribe with water or soda or Gatorade or whatever, so long as it isn't red, because the dye could be mistaken for blood, I guess. Your doc will give you a list of what is acceptable.
Anyway, the procedure itself was a BREEZE! They started an IV line in which to give the anesthetic (it's not the tube-down-the-throat version, thank goodness!)
Doctors in Los Angeles these days knock the patients out, totally. I was completely "asleep" and it's great. You just kind of drift off and are pulled back from that "sleep" afterwards in the same fashion. We all wished we had that delightful "drug" at home! What a feeling!
Afterwards, I ate light for one day as there is a little bloating and gas, but again, it's not a big deal at all and is not painful or long-lasting. Honestly, if I hadn't seen the pictures taken during the procedure I'd have sworn NOTHING had taken place at all.
Go for it; you'll be glad you did. By the way, they took three samples to check for colitis but there was no sign of it. If they find polyps, they will snip them out the same way. You may or may not have a drop or two of blood within a week of the procedure; I did NOT, but they tell you it's possible. Again, no big deal.
Best wishes for a positive outcome! You won't like drinking the solution beforehand, but the procedure itself is easy to take. Insist on the "total knock-out" however; I understand if you are awake it's not so totally pleasant.