Unless you have put a ridiculous number of miles on it or it doesn't have the capacity to pull whatever you have now, a ten year old diesel should not need replacing. Just wanting to replace it for the hell of it is another issue. Have you thought about getting a lease return instead of something new? Better yet, find the model of this years truck you like and arrange with a dealership to buy a lease return of that model when they come up for return. That will let you see if the model has any issues and also let you get a few more years out of your existing truck.