Unbolt the area that has the oil filter mount. I think there are 4 bolts there. Take the oil pump gears out and look at the inside of the pump walls. If they are scratched then the entire unit is junk. Sure it might work when you bolt it up, but chances are that it will never make 40 psi oil pressure. Probably closer to 10-15 psi.
Four Wheel parts has one of the cheaper aftermarket units and I think they are about $250.