I don't know where you could look, maybe local electrical supplier that was in-business since then, or if the manufactruer of your equipment still exists.
The system is simple. 12 volt power feeds the light switches. The switches activate relays that activate the 115 volt receptacles or ceiling outlets.
Even if you find information about the system, it won't show how your particular house is wired. Just like how each houses circuit breaker box is wired differently. As ling as the breakers are sized properly, they don't pay much attention to whether the furnace is on breaker #4 or #16.
You need to find someone who is familiar with the maintenance of this particular system. They should be common enough that you can find a licenced electrician who has experience with your system. Pay him the $65 or $70 for an hour visit to go over your system with you. Ya gotta spend it somewhere...