I realize it depends upon age and mileage, but. overall. does a used Mercedes CLK series convertible require much repair if maintained properly?

No more than any other high end fun car. And they are fun cars!

it will take more maintenance and repair than most other cars- and, for sure, that service will be expensive, and will have to be carried out by specialists-

I think if you keep up on the maintenance they are fairly reliable. Mercedes has been useing the motor that in that car in several models for some time now and it seems to be fairly reliable. If the car is out of warranty just be sure to find a good indenpent Mercedes mechanic. The car your looking at is still fairly new so it should be free from problems as long as it has been taken care of up to this point in its life. On an ending note i will say once you own a Mercedes its hard to own anything else.

Amen to the above. Love them Mercedes Benz.

As what was said earlier ! Find yourself a good honest "Mechanic" who specialized on this kind of vehicles ! If u understand owning a Mercedes, U will appreciate having one, regardless of aged & mileage ! Properly Maintained is the "key" word ! They've been using these engines wayback ! The 350 engines have been missing for awhile then was brought back w/ more re-defined ! Watch for the 430's & 500's since it will be gone for awhile ! It will be brought back w/ much better technology ! That's how Mercedes have been doin for a very long time !

Check with 2010 Consumer Report Magazine buying guide page 171. I have a 2008 CLK with no problems mentioned in this column. Of course I have only 20K MI on this. Between 4 mercd I have put in 400k Mi. I am thinking of selling this and get a SLK or Glk. Good luck.