9K for a 300CD seems a high price for the condition you describe in the USA to me (but I'm no expert) - that's the kind of money they cost over here in Holland (and they are only that expensive because you don't have to pay road tax on them when they are older than 25 years old so you are "saving" about 1000 Euros a year)

Engine shaking could also be injectors as well as the mounts.