Does the radio turn on?

The amp would have been under your passenger seat. There would be a plug and thick wire routed from the radio to the changer and that would be the only wire at the changer location. If this is unplugged, the changer wouldn't work but the radio should still work.

If someone put in an aftermarket stereo system they may have cut the wires at the stock amp to splice into or rewired the car all together.

Check the connections on the back of the head unit. Check the wires going into the amp under the seat.

If those are good, you'll need to remove the door panels to check the wiring at the speakers.

You may want to do a continuity check from tip to tip of wires from the head unti to the amp, amp tot the speakers to insure they are good.