I have an '94 purchased recently and servicing all the winches was one of my first tasks. The Lewmar electric 58 mains were particularly troublesome and although it may or may not help you, wanted to share my experience in hopes it may give you a little more insight. I discovered that these winches on my boat can not be fully serviced without removing them from the deck. In order to remove them, I had to remove the drive motor from below decks. This was a fairly straightforward process of removing the four bolts that hold the drive motor to the flange that is in turn bolted to the collar that is part of the center stem of the winch. For your information, when I removed the four bolts that connect the motor to the flange, I was able to jiggle the motor and it slid right off the shaft that drives the gears in the stem of the winch. That shaft has a slot and a key arrangement. I uploaded a bunch of pictures of process to this site via the post "servicing lewmar 58 winches". If your motor does not drop off the drive shaft, then it is seized to that shaft. Did your pros try to pry it off the motor assembly from that flange?
Photo album of Winch service:
Amel SM117 '94