If you intend to do very specific work, the MB factory CD manual is useful. The Haynes and Chiltons manuals don't describe certain systems (climate control, vacuum, door mechanicals, etc.) adequately for diagnosis and repair. If you don't intend to do repairs on these systems then I suppose you don't need a CD manual.

The print quality is terrible even on a good laser printer. MB didn't use the print optimized option in Adobe Acrobat. The electrical diagrams in the CD manual for W126 are readable on screen, but not when printed.

The CD manual for the W126 doesn't cover the transmission, not even removal and replacement. The W123 version might be different but I doubt it.

The CD manuals on ebay for $10 might be copies. No reason to think they wouldn't work. This isn't a recommendation to violate copyright laws.

I can't speak for other CD manuals since I've never used them.

Sixto
91 300SE
81 300SD ... buy me