Jestah is the man you need to speak to, he knows shitloads on building, and can probably sell you some materials to make your first board, or at least point you in the direction of the best place to get some. Plus, he's in Aux like you and from what everyone else says is a real awesome dude, so might even be willing to give you a personal lesson or two (if you ask him real nice, and maybe bribe him).

Regarding birch, my understanding is that gaboon is just as good, less expensive, and easier to find in NZ - have a look in the boardbuilders forum for a thread titled 'materials' - pretty sure your question's been covered in there somewhere.