Yep.... shop prices around the net. Just be sure it's a from Chrysler/Mopar and not an aftermarket warranty. All the ones I've seen will be sold from a dealer somewhere.
I went with the Lifetime Max Care on mine (6.4 Hemi) but I don't think that's available on a diesel. The fine print is they will pay the price of the truck according to NADA if/when the repair exceeds the value of the truck.
I think statistically, the chances of big problems with less than 100-120K are slim. I mainly got mine for when I get up to 150-200K range. I got rid of my last truck around that mileage for fear of upcoming repairs. This time I don't care. I just drive it like I stole it :)