Replace 2010 Mercury Grand Marquis Computer
 

My car computer is showing wacky error warnings like oil change required one week after changing the oil. Took car into Ford dealership and they identified tire fault on drivers side front tire and told me the Driver Door Module DDM 9W7Z-15K602-C on drivers side was bad and needed replacing.
My first question: Is it standard to replace the original wiring harness plug ins or keep using them?. I cant find what wiring harness part I need anywhere. Ford dealership claims I have the wrong DDM which I got online much cheaper than the one they tried to sell me. I found the exact same DDM on a you tube video showing how to change them. Needless to say I dont trust that Ford dealership to tell me anything I can trust. My other question is could my bad car computer be causing the bad tire fault flashing error issue and other electrical issues like power locks, trunk, power mirror, dome light not working??