There are plenty of 24 hour servos around the place, particularly in capitals.
Your cost of living is going to be quite high in WA in general. All around the mine sites are particularly steep in price. But if you are fly in fly out you may find some cheaper places in Perth or Fremantle. You might also want to look for a share house since you are only going to be there for a week out of every month anyway!
On your predicted salary you should be able to live comfortably over here. I myself am about to make a move from close to a capital to outback Australia... lots of red dirt. But I suppose you have to go where the money is! It was a good excuse to buy my Nissan Patrol

I also wanted a Surf, but I didn't want an auto, and there was 1 manual one in the country at the time.
Not EVERYTHING is trying to kill you over here, and spiders are kinda a good thing, because they help with eating the 10 billion freaking flies! Just don't lift any tree bark, don't turn over flat rocks in summer (Brownies love to hide under there), and don't walk through long grass in summer. Simple!
Lastly, you should def start an Aussie slang thread. I hear that "Cracker" and "Root" mean VERY different things to an American. If you can get your hands on a movie called "The Castle", this would be a great place to start. Good luck with the big decisions ahead! You'll love the laid back lifestyle here.