Just to close the loop on this (and once again thank you to everyone) I bought a $79.00 rebuilt starter at Advance Auto (which was a MB original part for a 1981 US 300D) and we will see how long/how well this rebuilt starter stands up.
I traveled up to the car and did NOT have too much trouble (because a neighborhood kid had already taken off the old starter) putting the new starter on. The car cranked right over but would NOT start. A couple of shot of diesel approved starting fluid convinced her otherwise and we are back on the road!