HPOP oil
 

So I understand it runs off engine oil but does it pull it from the pan or is it seperate and if seperate is there a certain type/weight of oil I should use to fill it up if it's low?

no its not separate, the low pressure pump feeds oil from the pan up to the HPOP, and it shouldnt be low unless a pump is weak i believe, (but i maybe wrong) you might wait ta hear ta see what someone else has ta say also LOL

Above is correct. It is all one system....

The oil in the pan goes through the LPOP to the HPOP res through the HPOP towards the injectors and then back down into the pan.

Ok just needed to know if it needed a seperate amount of oil since the PO did 2 things to this truck: jack and chit

lol, you're on the right track, change the oil, start the truck and you just changed the HPOP oil.