I have a similar thread out there somewhere where I replaced the motors in an Amazon-sourced 4-position winder. The motors that come in these winders literally cost less than $1 and the failure rate is high. Here's the original thread:
I thought I'd quickly type this up in case it might help somebody. About a year ago I accumulated a few more automatics and it began to be a pain to have to keep winding and resetting times/dates, so I figured it was time to upgrade my winder to one with four slots. In a moment of cheapness I...
www.watchuseek.com
Essentially, if your motors have indeed failed, you need to grab the part number off them and cross reference. I found that many of these motors are made by Mabuchi, which are junk. I replaced them with a bit higher-quality motor (that you can still buy cheaply if you're patient and willing to wait for slow-boat shipping) and they are running nicely 5 years later (and much quieter than the originals.)
As to how to disassemble, sometimes they hide the screws under small stickers and in my case, the entire top portion just lifted up and was hinged on one side.