Possible 240D differential leak

[240Joe]

I just noticed that the differential on my 1980 240D has oil on it, and accumulated grim, as if there might be a slight leak. However, it isn't leaking enough for any oil to drip on my garage floor so it can't be too bad yet.

I've never checked or changed (if that's possible) the diff oil. Is it worth the looking into this a little more. How do you get the plug out? What type of oil is needed? The car has 224kmiles on her.

Also, the axle boots are starting to look pretty old, with slight cracks, but none all the way through. Any recommendations on when the rear axle boots should be changed...or just wait until one opens up and then get on it?

Thanks for the info.

Joe