Front main seal if you have efans or a shit ton of clearance:
-turn motor to top dead center
-pull e-brake, put car in 4th or 5th. Now the engine won't turn
-remove all your belts
-remove 27mm crank bolt
-pray to God that your pulley remover doesn't hit your radiator
-remove pulley
-pry out old seal with a screwdriver
-install new seal with a drift, large socket, and/or very carefully
-reinstall pulley making sure that woodruff key is still in the crank and the slot is aligned
-tightening the bolt presses the pulley. Final torque of 100ft-lbs or so.