Cadillac Repair: Wont start because of security system, cadillac eldorado, ohmeter

Question
    I have a 1991 Cadillac Eldorado. recently I replaced the battery and after having charged it I got in to start it and the Information Center displayed a message saying that the car could not start because of the security system. I look in the owner's manual and it tells you of a process to wait three minutes and try again. I have done this several times, it does not work.
    The dealership claims it is a problem with the security device in the key. I have two keys and both have the same result, the car will not start. The dealership eatimates $600.00 to fix.     
    The car is currently not in use and I had been trying to sell it so, I do not want to spend that kind of money, plus towing exspenses, on this car.
    Is there a way to fix this or to disable the security device preventing the engine start? Can you tell me how to reset the computer?

Thanks  

Answer
Hi Julie, Wow that is sure alot of money to spend on 2 keys and haveing the ignition lock cylinder diagnosed and replaced if that is what it needs.
  You might have some success if you take a cleaner such as peroxide or other mild cleaner and wipe the key pellet on both sides. The fact that you tried both keys probably means that a cleaning won't help because the wire comming down from the ignition switch has flexed in half.
   Now for the low buck repair. Take your ohmeter and put a lead on each side of the key pellet to get a reading. Then go to Radio Shack and buy a pack of 1/4 watt resistors as close to that reading as you can. Then back to the car remove the panels under the steering column so you see the bundle of wires and look for a 2 wire black connector that has 2 small white wires in an orange covering. Cut the wires on the steering column side of the connector and then attach one wire to a side of the resistor. Then tape it up so the resistor can't touch metal and turn the key and the engine should start. If you can do this yourself then this will cost you $3 tops otherwise maybe an hour at a shop. The downside is anything that turns the lock cylinder can start the engine now but with a cost savings that might be worth it. Hope that helps. Bill