Having purchased the full version of All Data in the day between 1993 and 1996 at a $ 6,000 buy in and $ 2,000 per year, coverage back then was spotty and generic for a less common car. No idea if it has gotten better for what you have over the years as there is little incentive to update older cars.

The big plus was access to wiring diagrams, most everything else can be found by digging around on the web these days.

Have you looked at the OE MB info on disc? From what I recall is was ~ $ 100 but don't quote me. There might even be a official MB online version.