An update, and a question...
A guy from GAHH called me back (he'd been out of the office) and addressed my concerns. The color mismatch he felt would go away if I put some leather conditioner on it, apparently that brings out the hue.
As to the other issues, he offered to take a look at it if I sent him the whole armrest. So I'm happy about that.
But, I don't know how to detach the armrest from the seat, and couldn't find any good instructions with a search. Has anyone done that ('92 300E or similar)?