Blade, before you go out and buy this 'fully sik' go-kart i suggest you contact the Australian Karting Association first.
Racing is split up into classes. Therefore, all engines must be of the same displacement and usually, the same make.
The Clubman class is probably the best for new drivers.
The costs involved with this class are relatively low but remember, while Go-karting is one of the cheapest forms of motorsport it isn't actually cheap.....
As for a chasis, there are many good makes out there but I would suggest looking at either a Tony Kart, Arrow or a Mike Wilson.
Good luck mate.