Alrighty! I sat down and got to work on it today... The cover popped right off with a light tap from my rubber mallet! :D
Just as I suspected, it's full of goo.... There doesn't seem to be any rust, just sand, and tar that used to be grease. I hosed the thing down with penetrating oil, and I can turn it now, backwards. I.E. I can spin the fan by hand and the crank will move, but it's not free enough to turn the crank to spin the fan. There's a bunch of dirt in the bottom of the gear housing, so I have to remove the fan-shaft to clean it out well.
Other than that, it looks to be in fine mechanical shape. I'm almost certain I'm going to have to replace the ball bearings on the back end of the fan shaft. They look pitted, but I won't know for sure until I can figure out how to get the fan shaft out of there... Guessing I'll have to take out the other gears first, but I'll do some research and figure that one out.
I see the gears appear to be brass, or bronze... so I'll have to be careful what grease I use to lubricate the thing back up... IIRC, automotive grease eats brass and bronze.
Was somewhat surprised when I popped off the fan shroud... looked almost like under my lawnmower deck! What DID this thing go through? Or, would that just be the result of coal dust getting sucked into the housing?