Although I live in MD now, my family has always taken our cars (from a '68 Impala convertible to my 87 420SEL) to Manfred's Automotive & Transmission, 648 W. Coolidge (602) 264-3606. Manfred is a great guy, does honest work and always for a reasonable fee. Can't recommend him more highly. He worked on the AC (among other things) on my 420 and while he is not a just Mercedes guy, he has owned more than a few and does quality work on them.

John
87 420SEL
00 C230K
00 A4 2.8Q