Also, make sure that all the service/repair history can be found. Usually, if the car is serviced only by MB dealers, then they should have all history on data base. See what repairs have been done. Some of the components may be wear out and are not changed yet(distributor caps, wires, plugs, engine mounts). Also, some of the earlier W140s have close-assist failed pre-maturely, and it's big bucks for it.
Hope you enjoy your new MB....