There is not much that you can get into because the mainsail furler is a sealed unit.
On hull 425 there was a standard oil seal right at the front of the furler which I didn't notice because of the leaking grease, it simply pulled out with a piece of wire, the original seal was cracked so I pressed in a new one in and the leak stopped.
Unfortunately I haven't been on the boat for one year so the details are vague but it was simple.
Like you I took the furler to machine shop to inquire how to open it up and it isn't possible, it is a sealed unit.
Br sure to tie off the mainsail foil inside the mast before you start as it will slide downwards very quickly if not secured.
Sea fever of cuan