Hello, I have just installed an aftermarket Head Unit in my 2004 Chevy Express

I did this on the cheap by wiring in a relay triggered by the power window RAP. I have no chimes now which I thought I would not miss but I have left the lights on 4 times now. I would like to wire in a warning chime into the Key Sense circuit and the exterior lights circuit. In hindsight I should have just forked out the 150 bucks to get a module for this truck but I thought I'd enjoy the experiment. Could you tell me which wire from the ignition would be the key sense and how I could wire in a second relay to the light circuit to accomplish the task at hand without blowing up the BCM?