The tech will have to pull your engine to install new heads. It varies, but you are looking at upwards of $2k, plus the cost of the heads, if that's what it is. Your best bet is to also have ARP head studs installed at the same time. You can drive it with blown HG's, but you should have this concern verified by a Ford diesel tech soon and have them explain it to you so that you can make an educated decision.
Good luck!