Copeland33

I just bought an 83 rx7 from some guy, he told me the stereo didnt work and i thought no problem (as ive done 7 other car stereos). I opened up the dash and everything so i can clearly see all the wiring, and now i know why it didnt work. The guy before me has wires connected to more wires , conncted to MORE wires, that are attatched to absolutley nothing. This guy was an idiot and now i have this huge mess to deal with. I want to rewire everything right from the main source, but as going through it im still learning. Wondering if anyone can tell me where the main source that all the wires connect to so i can just rewire everything the way i want it and i know what the hell is going on, is this possible ?

i have printed the wiring diagram of the rx7 and my deck, but with the same colored wires going everywhere and attatched to eachother , im having troubles determining which are the stereo wires and which are not.