Did you remove the 2 transport screws on top of the radio before installation? This will prevent any CD/DVD from ejecting from the radio.
If the CD/DVD will not eject, with the receiver powered on, use a paperclip and press and hold the pinhole-sized reset button (see the instruction manual for your models reset button location) until the receiver shuts off. Anything in the disc player will eject at this point, correcting the problem.