Oscars Auto Service. Serviced my Sprinter 2004 really well and he owns 1-2 sprinters himself so he is very familiar with the model's trouble points.
He is in North Miami area and although its a "low budget outfit" he did the work for half the cost of a dealer and he did it right.
There's also a sprinter mechanic in Hollywood. You can find him at miamisprinterrepair.com
(Dont know anything about them other than from the site)
Mike