I will give you my opinion. Do what you should have done prior to buying the car. Take it to a good independent MB mechanic and pay them to do a Pre-Purchase Inspection even though it's actually an after Purchase inspection.

This may cost you $150 , but save you more than that amount by telling you what you need to replace versus replacing parts blindly, hoping that you solve the problem.

If you are going to work on this car, then you need a manual. CD or Paper.

Also, when you post a question to the forum you need to state the mileage of the car in question.