Your downloaded content should continue to work, and your Wii points can be spend as normal. The primary thing to watch out for is buying local games in Australia for use with your Wii. The system is generally region-free, but third-party publishers are given leave to region-lock their games at their own discretion. You may also have trouble buying Wii points locally in a store and attempting to add them to your system, but buying them online through the Wii itself should work fine.