More Language Confusion

So I moved from the United States to Australia. Easy, right? Both countries speak English! I won't have any problem understanding them, or them understanding me. Piece of cake? Not exactly...
They speak English, yes, but have a whole lot of different words for things and that confuses me daily.
Am I walking on the sidewalk? NO! It is a footpath. Do I put gas in my car? Of course not - it is petrol. Post, not Mail. Splash back, not back splash in the kitchen. A pie is most often savory and filled with meat, not something you get with a scoop of ice cream at the end of your meal. A Hotel is not a place you can get a room for the night, it is a pub. Actually it is like a Sports Bar, as they all have a million TV screens showing different races you can bet on, and often rows of slot machines or "Pokies". However they also have Chicken Parma specials with which you get platters of food bigger than your head for very reasonable prices, so I can overlook the other things... 
And my favorite? Cotton balls are called "cotton wool".  I think they are confused, as it cannot be cotton and wool at the same time.

And don't even get me started on the spelling differences! Harbour. Colour. Authorise. My spellcheck goes crazy every time I try to type anything. It is going to take some time to assimilate.