In my opinion below are priority items:
1) Recall on secondary coolant pump + front driveshaft
2) Latest version (Index12) injectors and hopefully changed not too long ago as Index12 is not maintenance-free either
3) Hopefully new plugs and coil packs
4) Maintenance, i.e. is the owner doing regular enough oil changes, and whether the adjacent oils were regularly changed (tranny, x-case, front and rear diff, rear torque vectoring oils)
Otherwise pretty reliable truck...mine is 2010 and im loving it
