Since I haven't had to deal with the complexities of a colostomy, I think the basics would be similar to a urostomy. The biggest concern, as you've probably found out, is maintaining good skin integrity. Urine can cause serious skin issues, so everyone's routine is going to vary, and it will probably take a while to establish what works best for you. One thing I decided early on was that I could not tolerate attaching my bag to drain overnight. I found it much easier to get up and empty the small bag. I use a two-part system, which means changing the "wafer" on a regular basis, and this also is something you will determine based on how well your skin reacts. It took a while for me to settle on a routine that, for the most part, has worked well. I have to change the wafer every three days, but I have heard some people are able to go as long as 5-7 days. You probably have a schedule in place for your colostomy, so perhaps you could coordinate them so you would only have one change day.
I'm sure this is a difficult decision given what you've already been through, but I think the end result would offer you a better quality of life. You will be in my thoughts and prayers. I would like to remain in touch and know how you're doing. Sincere best wishes.