There are a lot of states where the Lemon law covers ag equipment.
So, they fixed your tractor with an aftermarket part? So, if you were to take it to another dealer for service, your warranty could possibly be voided? The guys here are right, no more Mr. Nice Guy. I bought a Harley once that was nothing but problems. This was in 2000, not in the dark ages of Harley. The bike spent three months of the first year in the shop. They broke every factory seal on the bike trying to fix this problem or that. I went back to the dealer, asked for the OWNER, and told him what was happening. He started with the line of "well, you did get to ride it for 9 months". That set me off. Contacted a lawyer, and the following week I had a new bike. Amazing what the presence of a lawyer does. Personally, I think they are all snakes, but a necessary evil.
Get a lawyer, get a NEW tractor. The integrity of yours has been compromised, and your dealer has replaced parts on a NEW tractor with non-New Holland parts.