Roy at MercedesHeritage is a great resource; so is John Olson at SL Market Letter in Minneapolis, and Brian Peters of Motoring Investments in San Diego. Don't forget listing it here in the for sale section here, and MBCA Star Magazine listings, and Hemmings... Have a good idea of its honest condition, value and what you want for it--be prepared for lots of questions and ensure you have a good set of detailed photos and be ready to take more.
Some weeks ago I put some people in touch with a friend here in Ann Arbor--car sold in 2 weeks.