Where would you find a free diagram that shows the correct order of plug wires to distributor for a 1994 Cadillac DeVille?

You Can get that from a Repair manual. If you go to the local library they probably have one. You may try Autozone and they may be able to give you the info ,if not they will sell you a inexpensive repair manual. I'm pretty sure you have a 4.9ltr engine for reference.Its called firing order. You will need to take the cap off and make sure the rotor is pointing to number one. The manual will reference this for you and show you which one on the cap is #1