Welcome to the forum! Well it seems you're both lucky and unlucky.. two free engines is lucky, but unlucky you had to deal with it. Perhaps it's a sign to move on? I wouldn't let this motor scare you from diesels... some are just bad lemons sadly.
With tires, you get what you pay for I believe. Even buying a nice mid grade tire is well worth it over some cheap knockoff set. So much is riding on your tires ya know... :D
2-3 MPG overall loss FYI is what I've noticed, even with the EcoDiesel. I don't have a garage currently that I park my truck in so I have a lot of warm up time in the winter, I personally don't care about the fuel lost if I can get in a nice heated cab.