Well, didn't know they were connected to Autozone... but maybe. I know I've used ALLDATA softcopy manuals for longer than Autozone has been around here in Virginia.
I've used an ALLDATA subscription for my 1996 S500 and have been very satisfied. Its not particularly intuitive to find things, but once you get the hang of it, its very good. Most of the procedures and pictures/drawings are straight out of the Mercedes documentation and are so marked.
Its much more complete than any other manual I've seen for the W140... although I'm sure the actual Mercedes WIS site is better.
Of course, ALLDATA is only 25 dollars... and ten dollars off of that per year once you sign up.
Hope this helps.

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KenP

1996 S500 W140 Coupe