cadillac deville theft code?

No, it's a lot different.  There are several things you need to consider when working with ANY GM vehicle thats relatively new...

Most of them have Theftlock systems, which means if you disconnect the radio or battery, it's gonna lock you out of the radio until you reset the code.  Also, with OnStar, it uses a new databus that most people find extremely complicated to tap into.  Most of the times, you can just relocate the factory head unit to a different part of the car using a Metra or Scotch radio headunit relocator.  Look at them on SoundDomain, they are relatively cheap and still allow you to keep your existing features like door chime and OnStar, since they are ran through the radio speakers.

As for resetting your theftlock code, google it.  Good luck, let me know if you need any more help/details.  This post was kinda rushed, I'm on my way to bed =P.

--mindctrl