My door lock has been hard to turn lately and the other morning when it froze up due to low temp the lock broke and my key turns freely left to right in the driver's side door lock. I took the panel off and it seems the round plastic piece on the backof the lock is broken because it fell off when I touched it. I was told it should be locked under the c clip at the back of the lock. I need to know if the plastic piece comes with a new lock and door assembly or does it come with the rod part it is attached to inside the door? Can I buy the plastic piece separately or do I have to purchase the complete unit. I can get a used lock assembly but I do not know if the round plastic piece is included. Does anyone have a diagram of these parts? thanks