no power

If the car starts then you have a short with the grounding wire, rare. If the car does NOT start, common for GM, then the main solenoid burned out and needs replaced. The main solenoid, Passlock sensor and ignition is all one piece, that thing you stick your key into when you go to start your car. If it is in the dash and not the steering wheel then it is held in with 3 bolts that can easily be removed if you remove your radio and go in through the opening where the radio was, after you remove the bolts remember to unplug the wires connected before removing from dash, it kind of looks like a little black canister and the main solenoid is molded to the back of it. The actual tumblers can be removed by pressing the locking mechanism at the side back so you can slide out the tumbler assembly and re- insert in to the new one so you can use the SAME KEY with the new one. I find it best to get one from the junk yard, they have many that still work because the stores are overpriced or have solenoids that are not OEM and cause electrical issues that drive you nuts until you figure out that the replacement ignition was not OEM. Good luck, and as a side note the tumbler assembly will have a little bar like magnet on it, this is part of your Passlock, if you do not use the same tumbler assembly with the same Passlock then you need to have the car to recognize the new Passlock or you will get electrical power back and car will not start because Passlock feature thinks it is someone trying to steal the car. Passlock reprogramming varies but reusing the same tumbler assembly and keeping same Passlock keeps same key and saves you the headache of the Passlock issue.

Is the ignition switch really mounted on the dash of this '04 car and not on the steering column?