Dear Two Idiots,
Alright here it is... first off I will apologize in advance it has been awhile since I have worked on one of these so some of the details might be a little fuzzy... Dont be discouraged the new canbus networks suck I don't care who you are!!
First find the amp and get to it... I think it is above the glove box towards the radio it is behind a plastic panel and is a pita to get to... the amp will have two plugs that plug into it one is the input and power connections the other is the speaker leads. Here are all the outputs from the amp
Speaker 1 FL+ DARK GREEN/YELLOW C2 PIN 1
Speaker 1 FL - DARK GREEN/LIGHT BLUE C2 PIN 7
Speaker 1 FR + GRAY/YELLOW C2 PIN 2
Speaker 1 FR - GRAY/LIGHT BLUE C2 PIN 8
Speaker 1 RL + DARK GREEN/LIGHT GREEN C2 PIN 4
Speaker 1 RL - GRAY/DARK GREEN C2 PIN 9
Speaker 1 RR + DARK GREEN/LIGHT GREEN C2 PIN 4
Speaker 1 RR - DARK GREEN/GRAY C2 PIN 12
Speaker 1 CTR + GRAY/BROWN C1 PIN 3
Speaker 1 CTR - GRAY/ORANGE C1 PIN 12
Speaker 2 FL + GRAY/ORANGE C1 PIN 1
Speaker 2 FL - GRAY/YELLOW C1 PIN 10
Speaker 2 FR + GRAY/DARK GREEN C1 PIN 2
Speaker 2 FR - GRAY/LIGHT GREEN C1 PIN 11
speaker 1 should be the door speakers and ctr is the center channel and the speaker 2 should be the dash speakers.
You could also get the speaker wires same color right where they go into the door boots for each door... JUST BE CAREFUL!!! the wires for the rear speakers are the same color as the wires for the pyro charges for the seat belt retractors and they will each test out at 3 to 4 ohms!!
I would run the wires from your 4chnl amp to the wires at the factory amp and use the factory wires to distribute to the speakers... and then the RCAs from the D3 to the 4chnl ovbiously!
Anything else let me know. Test and verify all your wires before you connect and I am not responsible if this info is not 100% correct, that is why you test first!