For $20K, the E420 or 400E would be the 124 model with the v8 engine.
Most late model MB would have the same (so call big ticket repair). A/C eveaporator, engine head gasket, belt tensioner, O2 sensors, and the list go on...
The goal of this forum is to educate us how to trouble and repair what is broken on our cars.
Rather you like the look and style of the 124, or 140. If you like it, and the repair work has be done. Buy it, it's only a machine, they will break again.