A quick way to confirm that the belt is squeaking is to pour a little water on it while the engine is running. If the squeaking stops, it's the belt. If if doesn't stop, it's a pulley, etc.

When shopping for maintenance, there are some jobs, like shocks and basic air conditioning, that are about the same on a Mercedes as a Ford or Chrysler. So you might not need to limit your search to "Euro" shops for those jobs.

You might also find that the job will cost less if you have your husband deal with the shop.