I own a 2002 ML320. I have a "start error", the engine will not turn over with the original key in the ignition at position 3

. I also have a spare key that I'm sure was not programmed that I tried to start the car with that probably created the error. I have since tried to start the car with the original key (after the spare) but still get the same error. So, I "shorted" the K8 relay and the starter will turn over the engine (so I have ruled out a bad starter or solenoid). Not sure that there is anything more I can do to diagnose the problem (without spending thousands at the dealer). I'm open to suggestions though.
So I think my only "economic" solution is to go to the junkyard and purchase a new ignition "system", with a key included. Can someone tell me all the components I will need to get from the junkyard car to resolve this start error? I am guessing I at least need the immobilizer, DAS module, ignition switch and key. Anything else?
Otherwise, I am not willing to spend the thousands of dollars that the dealer would want to "repair" and program my current car.