Hey mate, firstly you need to drop off the drive belt with a 3/8” ratchet on the belt tensioner, then you will need to remove the 8 or so 12point internal head bolts on the front of the pulley. Once these are out the crank pulley is held on with a dowl into the the crank shaft. Spray some crc in behind the pulley and with a bit of wobbling with a pry bar and some effort it will come forward. You will the have to chilsle and bend the front crank seal to remove it carefully with out damaging the front engine casing.

re insatlling can be difficult with the radiator installed but depends on what your plan of attack is with refitting the front seal mate.
let us know how you go.

Hey mate if your referring to the small hole located to the upper right hand side of the crank pulley near the right cylinder head it a drain hole for under the intake manifold, if this is the one it means you have a large oil leak under the manifold, usally the oil filter housing return tube oring or the feed plate next to it.
can you take a pic of the hole