I received the machined part from Russia yesterday and have transferred the bearings to it. Today, I will be repairing the ribbon cable that runs from the yaw motor windings to the control circuitry.
The previous owner took it apart and made a couple of mistakes. He tore the ribbon cable that I just mentioned - there is no replacement part available for it, but I can repair it. There is a magnetic nut that needs to be positioned quite precisely because it's what the gimbal uses to understand when it is pointed forward. He removed it without marking its position at all. This will mean I am probably going to have to take the gimbal apart multiple times to adjust the alignment.
What didn't get broken is the long ribbon cable that spirals around the yaw axis support. I bought one, just in case, but I won't need it for this repair.
I'll post updates.