Welcome! If the motor goes and your tuned, your warranty is likely gone. Overall, I can't say what's the best year to buy, but the newest maybe might be the best answer here. If you're buying one used, make sure you have the maintenance records and it's been taken care of..
Welcome! As always, go with your gut. I would research the forum here, YouTube, and even ask a few people you see in town with one to help you gather your thoughts.
If you do go that route.. make sure you have some kind of warranty just in case something major happens.
The chances of issues are much greater with an EcoDiesel over any other new modern diesel right now. Just my opinion.. if you have a warranty and not totally dependent on your truck and get a good deal, then go for it!
Welcome! 6" lift will be a good amount of lift. You're fuel mileage will drop at least 4+MPG also. But hey, smiles per gallon is more exciting than miles per gallon.
I'd search around and compare the stance to both of them. I had a 4" on my last Chevy truck, and it was more than enough after...