I am a first itme diesel owner as of July. My truck is a 2013 3500 duramax with 57,000 miles on it. Recently it pulled a NOx code. Teh diesel shop I am taking it too said new sensorts are $370 a piec...
Don't know about the Duramax, but mine did require a tune. It was actually turned off, but I went ahead and let the couple of extra pounds fall off the truck. It does run better and I probably get a little better mileage with it, but with the straight pipe, it's kinda hard to stay off the skinny pedal.