Hi! I did a CP in merchandise. I'll share what I can, but if you have any specific questions, I might be able to be of more help.
The job in general kind of depends on where you work, parks, resorts, or Downtown Disney. Downtown is one of the busiest places, but you're basically guaranteed to have a night shift there. Parks are naturally also busy, busiest in the afternoons and nights, which is when most CPs will work. If you're in a park, say Magic Kingdom, expect to often work until midnight or later. Resorts are the calmest. Still kinda busy no doubt, but you can predict the busy times, mornings, lunch, park closing. And some resort shops close really early, which is wonderful.
Hours vary. 40-45 hours is pretty standard, except for during the busy season. Honestly, during 4th of July week, Christmas, Thanksgiving, things like that, 60+ hour weeks, 2 or 3 weeks in a row are not uncommon. Your day(s) off vary every week, and unless it's swamped, you get 2 days per week.
I can't think of anything else real basic to tell you, but if you have a specific question I'd be more than happy to help.