What diagnostic CD's are you referring to? Do you mean the factory service manuals? These are available online now, for free:
Official MB Model 124 Service Library (with annoying Flash interface) :
http://www.startekinfo.com/StarTek/outside/12264/?requestedDocId=12264
Mirrored version with awesome HTML interface courtesy of Steve Nervig:
http://www.w124-zone.com/downloads/MB%20CD/W124/Main.html
For diagnostic trouble code info on the 500E, use this document with your hand-held blink code reader:
http://www.w124performance.com/docs/mb/diagnostics/DTC_List_W124_M119.pdf