Radio Theft Lock Code? Help!

I purchased a Cadillac CD player off eBay for my sister's 1998 Cadillac Deville. She received it today and tried to install it. When she did she got a message regarding the Theft Lock Code. Does anyone know what this is or how to bypass it? I would be happy to send you the link to the eBay website or my Pay Pal receipt showing that I did pay for it. The dealerships said they would charge her $100 for this code. I saw on another thread what number to call for a Chevy, but nothing for a Cadillac. Any help is greatly appreciated. Thanks!

Have a look inside the "old" radio - there should be a EPROM memory (a big integrated circuit "bug" with or without a small round or square window on top) . Take that one off there and replace it inside the "new" radio. It should work.