Depends on use of course, but the 300K figure earlier is a good estimate. More stop and go, lower mileage but if on longer trips 500K is possible. As far as parts cost go, LOTS. Check some motor rebuilders for replacement cost, and compare to gas engines. That will give you an idea of the diesel parts premium.
I replaced the sleeves, pistons, rings. seals and gaskets in a similar 4 cyl Mitsubishi truck recently. $2000 in parts and machine work. Note, that did not include any crank or bearing work.
