We have shops here, in many cities, that specialize in convertible (power) tops - most of these systems work in similar fashion no matter what manufacturer made the car.

I would look for a shop that has experience with these problems. A price is hard to quote, with taking the trim off and putting it back together, and time to inspect for leaks, I'd say a two hour labor charge would be reasonable. Over here, that would be $180US to $300US.

Remember the car is mostly a Mercedes, one thing I like to do is find an independent shop that works on a lot of Mercedes - such shops are usually very experienced with the Mercedes designs. Mercedes DEALERS do not always want to work on these cars, because they say "Chrysler" on them, this is not always the case, but often is.

I imagine Mercedes are quite common over there!