4 years old question but I'll reply for anyone who finds this question looking for help:
It's a single hex bolt under the eyepiece end of the polar scope to remove the RA gearbox. Once gearbox is removed, the cover can be removed from that point with a small screwdriver.
You will need a 1/16" hex wrench to tighten the spur gear to the shaft.
Edited by Tom Stock, 12 February 2020 - 05:57 AM.