how do i disable the stock amp becuz now i've got an aftermarket cd player? or do i not need to?

 

yes you have to disable it... you will have to run new wiring from your aftermarket head unit to the speakers in the doors and rear speakers OR run new wiring from your head unit to the back where the amp is located and tie into the amps outputs that run to the door and rear speakers. Eitehr way will work, but new wiring directly to the speakers is best.