stereo problem =/

I know this question is probably elementary to some of you and maybe because since you cant see the car, its useless in me asking this question, but I am 16 and just bought my first car, a 95 Monte LS and it has a pioneer 6 disc cd changer in the trunk. I am pretty suer this is factory installed because of the fact that the stock radio is still in there as well. Anyways, there is no power getting to it and i was hoping that someone could help me out with this. The screen is not turning on in the front but the stock radio does turn on and is fully functionable. Can someone please fill me in on how the factory installed disc changers are hooked up? The engine in the monte was swapped with another...could this be why there is no power getting to it? ANY information is welcome! thanks =)

It's possible that the previous owner had an aftermarket stereo in it and swapped it out before selling it, if your backseats pull down I would check the back and follow the wires to see if its hooked up properly.