I am about to buy a 2003 Dodge 3500 4x4 Diesel with all the goodies Leather,etc...?

the only thing is is that the truck has 180,000+ on it now i know that Cummins Diesel's with run for a lifetime but all i want to know is if there is a place that i can buy a new Cummins Engine for or if i should just call a Dealer and ask them?