so, if i install the new cylinder lock and plug in the wires to the vats connection, is that all I need to do or do I have to change out the entire module? What part of the system reads the resistance?

 

That is all that you need to do as long as you have a new key with the same resistance value as the old one. The contacts in the lock cylinder read the resistance value of the pellet and send it to the VATS control module which in turn verifies it to the ECM.