There is no steal price without determining whether the car has records, and has had the biggies replaced already. Even at free, you could end up with thousands to fix things like the inevitable head gasket, wiring harness (a problem your '90 doesn't have), A/C issues, water pump, belt tensioner etc. I don't know that the evaporator is all that common, but I can guarantee the A/C compressor will be at some point.

The three 300E's I have purchased all had some major work receipts in or around 80 to 110K. Also I don't really see the attraction in less power. But then again I don't know if the 2.8 is the M104 engine.

Steve