I'm assuming the in-dash CD player looks something like this?
or is it a single slot player with tapedeck on the top of the center console stack? If this, then it's not a six-disk player.
For the first one, I would think that you would just press the button of the CD that you want to eject, then hit the eject button.
However, in either case, removing the fuse or removing the negative batter cable temporarily should pop out all CDs and reset the device. Just be sure you have the radio codes if it asks for them.