Wow! Sounds like you are in the same boat as I am! I also have a 2006 Dodge Megacab Laramie with the 5.9 and I am looking at the TDI for my daily driver.
To give you an idea on pricing, my local stealership has a TDI w/Nav, auto, and JTS appearance package MSRP at $26,741 and a "special"...