Unfortuately it sounds like the eject mechanism failed. I can honestly tell you, you will pay more to have the unit fixed than to simply replace it with another GP/ACDelco stereo or aftermarket unit.
The only way you would get the CD is to take the HU out of the car and tear down the CD unit to dig out the CD that is stuck. I am not sure how difficult it is to tear one apart, but I am sure it is not a walk in the park. And I can not garuntee you will be able to successfully put it back together in a working order either.
It is just cheaper to check Ed Morad to see if he has any units available to replace your current one (if you want to remain stock) or purchase an aftermarket HU.
Sorry I can't be more helpful than that
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