I bought a 1997 Aurora with no door key, just an ignition and a remote. I asked an ebay seller of keys, and he said the door key should be the same cut as the ignition with no chip on the key. Is this true? If not, can I get one from the dealer?

I have a '97 also. the ignition key and the door key are different. All the dealer need is your car's vin number. And he should be able to produce a door key. Might be around $27 dollars. Try a cadillac dealer.