As a non-professional mechanic, I've learned how to utilize the services of a professional. A proper diagnosis is absolutely necessary to making the correct repair. If money is an issue, I'll simply contract with a professional to perform a diagnosis of the problem ONLY. Usually, the cost is minimal and then I have the necessary information to know what parts to purchase, factory manuals to consult, etc etc to go ahead and perform the repair service myself. Just make sure the mechanic knows Mercedes Benz automobiles and has the diagnostic software.