Since we're on the subject of software I came across a copy of Carsoft v7.4 which supports all Merceds engines before 2004 I believe. I'm not sure if it will work for out car but it's "free"
Carsoft MB 7.4 (download torrent) - TPB

The one nice thing I saw is that you can reset the service meter and even adjust the counter for it. It seems a lot easier than waiting for the stars and planets to align so you can reset it manually. Bluetooth ODBII adapaters use the same protocol so once you figure out the COM port you're good to go.