Thankyou mach4. I also agree that it's a bear to get apart. Yesterday I tried the same, ie to split the casing to do the same investigation as you. My approach was to pry the casing open starting at the power cord end. After removing the grommet with a pick and trying to pry open the case using leverage of a pocket-size snap-on screw driver, the casing started to split, but not along the seam line.
I had some time yesterday so I took the motor which I had removed the scew-adjusters from and attempted to get the motor to run up/down left/right in a no-load senario. It worked flawlessly doing the left/right but up/down worked temorarily and then stopped. Motor appeared to have stopped and would not work in either direction. After jabbing the screwdriver into my hand and seeing a little blood, I started to come to my sences and came to the same conslussion that Mach4 did, this probably isn't worth fixing for it's not meant to be a servicable unit!