Most RV manuals are generic. The specific component manuals (fridge, stove, water heater, etc) can sometimes be found on the manufacturer's websites. Not sure about a trailer from 1977, though.
My best piece of advice to a new owner is to take a few nights and camp in your driveway. Have on hand pencil and a notebook and start jotting down your thoughts and questions.
Being new to RVing, it would be useful to you if you would take a few hours and browse the forum and feel free to post any specific questions. I'm sure someone can help.