Last owner apparently not a big fan of changing the oil

2 ways to go about this:

1) Clean out the valve cover, loosen up the valves and take the rail assembly off and clean it out..with upper looking cruddy, makes me wonder what the inside cavity of the oil rail looks like.... clean the upper and drain the oil...put the plug back in the pan and then flush the system again with a mild solvent...let it sit for a moment.. drain again. Put fresh oil and a good filter on it with something like MM oil added in...Readjust valves and drive... Change the filter every 1500 miles...Repeat every oil change until flush out isn't chunky/black tar-ish anymore.

2) Just clean out the valve cover, change the oil + add something like MM oil and change the filter every 1500...Should eventually get clean.