As I remember, you need to remove both the disk cap on the large gear and smaller gear by drilling a hole in the center and using a sharp pointed tool to pry them out. Once out the larger gear will come out of the casing, allowing the smaller gear to be removed.
once you've fixed whatever your problem is, you can push the caps back in and use some JB Weld to close up the openings you drilled in the caps.
What exactly are you trying to accomplish with this deconstruction?