i have several DVDs which had been offered by MBUSA which I believe are no
longer in production. The one I use for w210 models was pretty decent and
are excerpts pulled from the WIS documentation. The interface is not intuitive
for me but bearable when needed.
The information within was less so a step-by-step, photo by photo but it was
still geared for the model and not generic. I saw the same line drawings found
in the WIS repair service
ebay item # 201936019739
https://www.startekinfo.com/StarTek/outside/7594/?requestedDocId=7594
Buying and Maintaining a 126 S-Class Mercedes by Nik Greene
Mercedes-Benz W 126: Die S-Klasse - Das beste Auto der Welt (German Edition) by Heribert Hofner (if you can read german)