Replaced Thermostat Housing, Still Leaking: Help?

Okay so apparently I'm the last to know that the plastic thermostat housing is a piece of crap and ours broke so I bought the two-piece metal variety that comes with a thermostat at Auto Zone.

After some serious novice struggling on my part to get the old one off, I finally got it off and the new one on but it's still leaking quite a bit between the engine and the housing. The guys at two different Auto Zones told me that I didn't need any type of sealant for it when I bought the part earlier today.

The old one did have a rubber gasket that the new one doesn't have. Should I have put this on the new one? I guess I was dumb to assume that if it needed it the metal one would have come with it.

So do I need this? Would it certainly be a better choice to buy a new gasket? Or do I need a sealant of some kind?

Thanks

You mean the gasket to the head? yes you need that.

I went to the dealer and bought the o ring then slapped it on with no leaks