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Hold the trackpad button while starting up (straight after the tone) and it should force eject the CD.
 
Does the optical drive work, can you read from the CD? If so you could always create a disk image of the disc and burn it later to play with.

Then I'd call AppleCare and complain very firmly about you're service experience. You sent it in for repair and came back unrepaired with more damage, that's ridiculous!
 
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