02 CD Player Wont Play

last month I changed out the alternator in my Venture and of course had to take the battery out since they dont make it easy to do your own repair work. Since then my radio will play but the CD player will not work. It is a 6 CD player but when I hit the play button it shows an "error".....
Instruction book says to call the manufacturer for "codes"......I'm completely lost.
Any help would be appreciated.

Might try to eject the cd's and reinsert.

yep, tried that and any button on the CD I push it shows an error.......I have 6 CD's inserted in the player and cant get them out.....very frustrating!

Try pulling the fuse of the radio circuit, count to 30, and re-insert the fuse.