1997 120 hp force ,detailed tips on removing and replacing cylinder head gasket,do i leave the cylinder head cover attached to the cylinder head since it looks like its two parts?,and far as gasket sealer that blue stuff use that in addittion with the gasket? .do i put it on both sides of the gasket?.at that time with the cylinder head off should i use that decarbonig stuff do clean the head and spray into cylinders? small leak in gasket ,will the water damage the cylinders or any other parts?will those heads worp?how do i check? thanks