Have a look at
www.brasstrains.com
The owner - Dan Glasure - is a knowledgeable authority concerning brass models.
Jstube--
I don't ever recall seeing any exploded parts views of Tenshodo steamers, at least, and I have several that I bought new back in the late 1960's. Disassembly is done with 3 screws for the most part--one under the cylinder saddle and two at the back of the cab, and the entire boiler lifts off of the drive mechanism. Very easy to get into and work on. I don't know about the diesels, though.
Vapeurchapelon's advice about contacting Brasstrains is definitely worth taking. I do know that there is a new catalogue available on brass locomotives and their manufacturers, but I understand it's pretty pricey, and I don't know whether or not it would offer any exploded views of the locomotives.
Tom
Tom View my layout photos! http://s299.photobucket.com/albums/mm310/TWhite-014/Rio%20Grande%20Yuba%20River%20Sub One can NEVER have too many Articulateds!