If you look on Ebay you can usually find these types of manuals on CD Rom, and there are a few people who can answer good technical service questions. However, most people (myself included) consider the original controls to be obsolete junk at this point. I ripped everything off of the junkyard Boss3 I bought and installed Gecko drivers for the original steppers for far less money than I'm sure it would have cost to bring the original circuits back to life.
http://www.runryder.com/helicopter/gallery/2598/