Well, there's probably more then one place to send the Becker for repair, but the best place to send it is back to Becker in New Jersey, where they maintain a repair shop. They are one of the few Mercedes suppliers dedicated to preservation and restoration of nearly everything they ever made.
Contact Ed Ebel at EEbel@harmanbecker.com and he will provide you with pricing, shipping instructions and might even do a little troubleshooting with you to ensure you have not overlooked anything.
Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored