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...
You don't want to piggyback over a custom ECM tune. That's the old school way of doing things back when tuners didn't have the know how or access to the correct tables to create a good tune.
I'd like to see GM's book hours for that trans drop to replace the belt. I've heard a few say it's a bit easier to do it GM's way rather than how Ford does the new 3.0L.. so, pick your poison! :D