Before moving to North Carolina a few years back, I took my Benz to Amoskeag European Auto. They are located on 599 Front St. in Manchester. Their phone # is 603-669-7750. I believe Pat MacCarthy is still the owner/tech. Prices were fair and Pat gave me a little advice from time to time. He converted my a/c 4 years ago - still works great even here in NC.
I also purchased a used vehicle from him... that transaction could have been more pleasant>