Generally, just the fuel hoses from pump and the fuel filter cannister need replacement. Its just bulk diesel rated fuel injection hose, about a foot. There are some lines at the tanks selector valve but its just diesel rated hose.
That is almost certainly going to be caused by the degrading of the rubber pieces that help secure and seal the metal lines to the fittings in the heads. There is no need to replace the metal "Y" assembly(not that they are available anyway). You only need the rubber sleeves. This is what is needed.