Looking for a mechanics opinion on this subject. I have a 99 E320 that I inherited from my deceased father in law. It runs fairly well, however, my mechanic has mentioned that sooner or later I will need to repair the rear main seal and the catalyst x 2 ! I'm looking at several thousand dollars !! The car has approx. 200k miles. I thought about replacing the engine with a used one w/lower mileage. I have seen many advertised (i.e. ebay and other websites)with low mileage. If I'm able to find a reputable source with (hopefully) a warranty would you recommend replacing the engine with a newer one with less miles (40k-50k)? I'm curious what the (approximate) cost would be to replace the engine? Can any of you mechanics in "Benz world" give your opinion? It would be greatly appreciated!