a couple of the nearest MB dealers and see what they would charge to send out a tech with the scanner to go over the car and tell you what you face?
It won't be cheap but neither will transporting the car to the dealer for the same service and you can be on hand to get your questions answered. (You could also call 1-800-FOR-Mercedes and see what they would do for you.) As part of the service get the dealer to agree to get you any service info on the car which is available. It would be helpful to find out what this car has gone thru in the past.