What we would recommend
1. Definitely buy a good travel book. We had a Lonely Planet: Queensland guide that worked very well.
2. Plan on driving unless you are going to stay in Sydney. They tend to rent a lot of manual cars.
3. Do whatever it takes to get to Fraser Island. Maybe our pictures convinced you, maybe not. But it is truly an experience unlike any other. Spend a minimum of four days if you want to see everything and relax along the way. We purchased our flights well in advance so we were stuck with the two day trip, which wasn't nearly enough.
4. The low cost airlines are pretty cheap if you buy tickets before you go when you are in the US, but four times as much if you wait until you get down there.
5. If you are going SCUBA diving, which is a blast, see if you can get your certification before taking the trip. Then when you go diving, you'll be comfortable and will concentrate on seeing the reef and not worrying. If that doesn't work, you can get certified while down there for around $200-300 in as few as three days.
Some words you'll want to know: tucker, bushtucker, bushtuckerman, no worries
Or email me: firstname.lastname@example.org.