There are several locations on the HPOP that can spring a leak. Some can be repaired with the pump in the truck, a couple require pump removal. The removal process isn't as bad as you would think. You can just google "HPOP Removal" and get lots of info and step by step directions.
Bob at dieselorings.com will have everything you need, and is a pleasure to do business with. I can't recommend him highly enough.