I had an ileostomy for 8 months before having my colon and rectum removed, so you can have a colostomy and still keep your colon and rectum even though you aren't using them.
What disease do you have? Is it Crohn's or Ulcerative Colitis? As long as you have active disease, you are going to feel some pain from it. It is lessened, however, when you're not using the diseased parts. If they don't get better after having the colostomy for 6 months, you should consider having the diseased parts removed.
I didn't think the mucous was a big deal. You just feel like you have to go to the bathroom, so you sit on the potty and that's all that comes out. From what I remember, it only happened once every couple of days, which was no big deal after having Crohn's and going 20+ a day!
I don't remember a lot of pain with the ileostomy surgery, since there wasn't a large incision to deal with. The only frustration I had was waiting 10 days for my ostomy to start working. I could only eat ice chips, and that got old real quick!
The most painful thing I do remember was changing my wafer for the first time and pulling the little blonde hairs out on my stomach one-by-one. I highly recommend shaving your stomach to the left of your belly button before surgery. That's where the wafer is going to go, and I'd like to spare you that unnecessary pain.
As with any surgery, it's recommended to give yourself 6 weeks off work to fully recover.
Dx'd Crohn's in '99 at 28. Proctocolectomy and ileostomy in '06.
Disease-free, medicine-free, and very thankful to be healthy again :)