Hi again, PeterB40.
I had my shaft seal replaced around the 5 year point as preventative maintenance. It was giving no trouble, however. My yard did it over the winter while the boat was out of the water, so unfortunately, I can't tell you how they did it. I am fairly certain it has to be done from the inside and I'm about 99.99999% certain it would have to be done while the boat is out of the water.
I asked the factory before having this seal replaced and they sent me the information below. It's for a GL33. Don't know whether it might be the same for you or not. My GL33 shaft is 40mm.
Factory comment:
[FONT="]Comment from Seaway: Shaft seal you can use any that will fit. Most common can be from Volvo Penta. We use Tormarine products: Stuffy box | Tor Marine[/FONT]
[FONT="]It is 40 mm shaft diameter. So stuffy box adapter is p/n: 1340000 Adapter for stuffy Box | Tor Marine Based on this you can choose suitable seal.[/FONT]
My yard used a 40mm Volvo Penta shaft seal.
The seal is water lubricated. My yard gave me a tip to push on the shaft with my foot after spring launch every year until I see a few drips of water come through the rubber boot. If you don't do this, it's possible an "air pocket" can keep water from coming in and starting the lubrication process. I have followed this advice and have never had any problem.
I have never added a couple of drops of grease to anything in this region. Never knew I was supposed to. What you describe just sounds like they're trying to be over-protective of the rubber boot so there's no risk of it getting chewed up. So, I guess a drop of grease there certainly wouldn't hurt.
I have never had any problems with the vibration-damping components. I have never lubricated anything in this area, either.
As far as the shaft seal is concerned, if it's not dripping water into the bilge and you have no unusual vibration, I would absolutely not worry about it for your upcoming 800nm trip. Plan to replace at home, however, when the boat comes out of the water for bottom maintenance and/or storage.
Good luck and have a nice voyage!