There is a pretty good deal going on EBay for a Haynes manual for the W124 chassis. It is euro-centric, but has some useful pictures and information on routine maintenance. Also covers some engine repair.
Go to EBay motors and use the advanced search function. Search on "124" in the parts section only. I suggest you use the "words to exclude" to enter "fiat" as the Fiat 124 is a popular model.
EBay seller "cybertroll.com" sells this hardcover book for $20.99 routinely. Don't bid it up - another will come along shortly.
I have this book and the Mercedes CDROM and feel pretty well equipped - along with the tremendous help available here......