This was the last year of production for the W124 and most (but not all) problems had been been worked out. Ask to see the vehicle's service records. Obtain the vehicle's VIN and have an M-B dealer run a VMI (Vehicle Master Inquiry) for you; the VMI doesn't detail regular maintenance hx but will show any service MBNA covered under warranty and may help highlight trouble areas. VMI repair groups are numerically coded so you will need the dealer's help in interpreting the printout.
Pay particular attention to the climate control system - any prior repairs (in or out of warranty), esp. repetitive freon loss? Evaporator integrity is a known trouble area and renewal is not cheap.