yea you will have to put something on there to seal it if you dont have a gasket. i use permatex black sealant when i changed my oil pump and its seem great. just dont put much on, just a very thin line, expecially at the oil passages. just make sure you dont get any in the oil passages and plug them.
I always use the blue rtv silicone for clutch cover gaskets, regardless of it being a new gasket or not. I don't like the cheap cardboardy gaskets these things use so I take that extra step so I know i'll never have to take it apart because of a leak.