Hi! I know 2 places that work on them in Charlotte area.
South Charlotte - Eurofed Automotive, 5410 Old Pineville Rd, Charlotte, NC 28217 - 980-360-5868
North Charlotte - JSG Automotive, 4315 Pete Brown Rd, Charlotte, NC 28269 -
(704) 597-5950
Both treat crossfires in their system as MB but both have been great to work with and Eurofed works on more than just my Crossfire. The guys at Eurofed will take you if you call or walk in, their website does not.
I can't promise their other locations will take you but this one does. If you have any trouble you can say they were recommended by me if you want (Jodi)
also JSG is usually pretty packed schedule wise but if it's not urgent you can call to get on their schedule.
I have in the past had normal / not MB folks work on them like Griffin Bros but if it's anything complex they will just hand the keys back to you because they don't know Mercedes very well. I would probably steer towards MB folks personally.