Not a fair call at all.
Put yourself in their shoes, and just pat yourself on the back for getting the job done the way you did it. Good attempt and a great outcome.
But can imagine that if you were the dealership service manager with the information you presented, that their reasonable estimate was what you rec'd.
If they had known what you managed to get away with, and you had your tractor hauled to the dealership during the busy harvesting season, and then they found out your "trick" didn't work and could only split the tractor to fix it, you'd have been even more upset. They were being upfront with you as to the potential outcome, IMO.
The dealer isn't in the business of providing free service, that our spoiled entitled liberals are so expecting these days. They have to make money to keep the doors open. Imagine how a gov't service would handle taking care of you..