It's always a good idea to seek a second opinion and don't just stick with the big dealers, there are lots of independent specialist mechanics who are often more tuned in to problems than dealers.

I have my 1999 CLK 320 Convertible for 12 years , It is great car , fast, comfortable , stylish , good gas mileage , has 12 sparkplugs , 2 for each cylinder ,if you live in a city with good weather ...