Personally from my experience Mercs are good solid cars. All of it depends on maintenance and mileage. We have one in the family, a C200 Kompressor station wagon. Its done a lot of kms(over 100K) as a daily runner, so far we had only replaced the compressor and alternator. Everything else is working fine and the car itself has been a rock solid beast. All work on it has been done at the Agents and nothing has been spared—endless driving results !!! A bit expensive if you have to replace the parts like the ones we have done, but all in all a good car.
Check on all the service records, for accidents and also get an idea and if possible, do an inspection at the agents to be on the safe side.