Those 5.0L's are tough things, my '00 Explorer that I just pulled the engine to rebuild had been BEAT TO HECK before I got it, we replaced EVERY hard part in the transmission (the one part we didn't replace lasted 20k miles before it exploded... they drove it hard enough to STRIP OUT the rear spider gears), pulled the engine at 260k and still cross hatching on all of the cylinders and valve seats looked new, I ground the exhaust valves and replaced one push rod and rocker, the rest was fine... of course it needed all the bearings and a hone and rering but that is to be expected at those miles... I wouldn't be afraid of pulling the engine, changing the oil pan gasket, valve cover gaskets (might as well do valve stem seals too) and front and rear main...