It depends on the particular vehicle…… If it is a drivetrain that originally had a diesel option, its no harder than doing the same conversion in a regular truck/van. The eaisest method would be to find a wrecked/damaged RV with the diesel drivetrain and do the swap that way. You have all of the needed parts at hand, and a very basic road map of how to do it. Price? That is a HUGE varible.. That completely depends on your particular technical abilities, and the starting points.