Both filters do come with a new gasket, which should be replaced every time the element is changed.
Be sure to get the old gasket out, and check that there isn't a second one down in the groove. I have seen several trucks with double gaskets come in for service, and it is a sure recipe for a leak. You should be able to get a small pick or awl into the groove to feel for(and/or remove) a second gasket. Most of the time you will need a pick just to get the one out.
