The dealership should be able to look up the key code and vats code so long as it has never been changed, however there have been cases where the vats code is not available. I beleive you can only look up key codes back to 2000, the parts department deals with that. If you can not get a vats code it would have to be hooked up to a tool to simulate the vats and figure out what it is, thats assuming you have a valid key code.
Worst case scenario you have to buy a new lock cylinder, and have the dealership test the car for the vats code. Honestly this happens more often then not, and has to be done at the dealership because of the special tools. The lock cylinders for VATS come pre-coded and cannot be changed (maybe by a locksmith, but we don't).