There are numerous shops around the country that do instrument repairs. Here are a few: http://www.paspeedo.com/
I am partial to the second because I own it, but the first is Top flite. I would have added United Speedometer but I didn't have their site or Nichol's Speedometer because they don't have a site. United is in Ca. and Nichol's is in N.Carolina. Numbers can be found if they are more convenient.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician