If the wa580 is bolted to a Chrysler motor it is a transmission made stateside, you can tell by the finish on the transmission housing (off the top of my head may be other indicators)... If the wa580 is bolted to a mercedes engine it is a german built trans. They are the same thing IIRC the stateside built box has a rougher finish and the german box has a smoother finish. Both the same trans, just ones built by a high american and one is built by a german dude
the 3.0 does have the nag1 behind it.
Know that "reliable" has a price and the common repairs on the 3.0l can be VERY spendy. swirl valves are VERY common and just an indication of how crappy they are to do, some guys pull the transmissions to remove the turbo to access them... all hours you get to pay for
That said I dig diesel but dont work on em much, we have 4-5 other very solid diesel techs that make me picking up another skill catigory just stupid.