If you can get a car with a extremely good running condition. then you are in for a treat. Make sure to check, it's computer (ECU).
then, check for rust under the car, plus check for replaced parts, like suspension, axles, steering assembly, rear drive shaft, cooling system (radiator operation+thermostats), AC, ABS+Airbags(if present-check their lights when key is at ON position). check for aftermarket alterations on the stock assemblies, Do not buy a Mercedes with any other engine. as this option will disable lot of safety & performance features.
I know this is a lot to check in a car, but again you are buying old German car. If you think the car is perfect in all ways, then just before buying, only check if Oil filters, air filters, ignition coils etc are available easily in Peshawar, which are necessary for periodic maintenance.
regards.