I just picked up my new 2015 Laramie 3500 Saturday. I'm still going over a ton of stuff to learn about this truck but I did read where with the Cummins 6.7 the oil change interval could be as high as 15,000 miles. I don't think I'm going to be going that high between oil changes on MY truck. On the '06 we just traded off I usually changed the oil and filter around 6,000 miles and every fall I changed the fuel filter. Air filter every other year.
Get the diesel you'll love it. Plenty of power and torque when needed.
Dan