Recommendations for a Service Center for Jeep Grand Cherokee with a Mercedes Engine in VA or MD?

Hi, I have a 2008 Jeep Grand Cherokee. I'm trying to find a place to take it where they can work competently on the Mercedes diesel engine. They are always very kind at the dealers I've been to, but never seem able to completely fix the issues. Anyone have a good recommendation in Maryland or Virginia? I took it in a few weeks ago for a leak and they gave it back, saying they saw the leak but don't know where it's coming from so they just gave it back. It's still leaking and I'd really like to take it to another place. Thanks.