1 yes and a good gasket I've had good experience with felpro
2 that hole is there in case you have one of the toy heads that require that hole instead of the two to each side of it. If air is coming from that hole its a good bet your gasket is not sealing
3 I'm not shure if a local parts store will have them or not, but the Advanced Auto Parts store here carries copper gaskets that I like to use.
4 After taking care of 1-3 you should be doing good.
