W124 is a solid car, one of the best chasis ever made. Classic, ageless design. It does require a little more attention than some other cars.
Following are the week area's and approx. prices at MB dealerships:
Engine Wiring Harness ($800)
Engine Head Gasket ($2200)
Fuel Pump Relay
AC Evaporator ($3000)
Major engine components may last over 300,000 miles with routine maint.
I get around 20 mpg and no unusual smell.
I would recommend keeping a backup OVP and fuel pump relay in the car. Also, you can make a led/sw tool to check the codes for the various modules like the ECM etc.
94 E320 58000 Miles