YOU CAN BUY ALL THE PARTS YOU NEED TO FIX YOUR TRACTOR.
The person you’re replying to is absolutely correct. The only thing you can’t do is legally modify the firmware on the controllers because that is usually done to bypass emissions controls. There are 10,000 page manuals supplied by Deere to diagnose and repair every part of their machinery. I have used them many times. I have never taken a tractor in to a Deere dealer to repair for any other reason than “I don’t have time to deal with this right now”.
Jesus, the misinformation on this subject is depressing, as is the willingness of people to accept it without a hint of critical thinking or research.