There was a very similar question yesterday. It alluded to service manuals on ebay for 140 cars. I looked through 12 pages of MB manuals and didn't see them so I didn't reply.
On ebay you will find copies of copies of CDs for all the chassis that have such: 114/115, 116, 107, 123, 124, 126, and 201 (each a one or two disc set). You also can find real versions occasionally. There is no such manual for the 140 car but there are some things that could be found. One such thing often refered to on ebay as a service manual is the Model Year Update Manual. In 1992 a separate book was published to introduce the 140 chassis. This is a book an inch thick or more. For early 140s its a great sorce of info. For later years there will be a lot of misinformation and lack of coverage, its all there is though.
There also are many versions or copies of the info Access series of CD Roms available. These also were "introduction to service" training CDs (in gorgeous detail) of new systems and disassembly techniques. I am not sure whether there is one for the 140 chassis but I imagine there is. I can't remember how early they start but I have about 11 of them. my first were copies but I did get a second set of genuine ones through ebay along with a number of technician training packages which were boxes that included a model training text, training video and training CD (Access). I have a copy of the training video showing the dash removal on 140 so I imagine there must have been an Access CD for 140 also.
Bosch Master, ASE Master, L1
33 years MB technician