The Haynes manual is pretty good. It includes instructions to swap an
engine, a tranny, both combined, an engine re-build, and carb rebuild, all
your basic periodic 1million mile maintenance tasks and in between carb oil
re-fills, brake shoe replacements, lubrications, etc. Any Autozone can order
it for you for $14.95 US dollar. Probably you can find it even cheaper at
Amazon.com or eBay.
The Volvo Manufacturer's book (or "green book") is actually several books,
separated by the car's various sub-systems, such as Engine, Brakes,
Steering/Suspension, Transmission, etc. These are not as easily obtained as
the Haynes manual, and will altogether likely be more expensive and more
difficult to collect the entire set.
There is no manual to show you how to re-build the temperamental blinker
switch, or re-cover the cracked dash pad, or upgrade to overdrive, or add
A/C, or convert from generator to alternator, or upgrade from 35amp to
55amp. But, if you found this newsgroup, you've got the right start. You
should also check out the 1800list on Yahoo Egroups. Mechanically, the 122
and the 1800 are the same.