lay over in Sydney
 

We are arriving from Fiji (in Sydney) at 11 a.m. and have another flight scheduled from Sydney to Cairns at 6:45 p.m.
We hoped to grab some public transport and head down to the harbour for a while. I assume we have plenty of time to do this.
What is the best method of transport from the airport and what is the cost?

Train from airport into city!

Cost is about $AUS10/head each way. Aim for Circular Quay station - on the harbour.

Hi, dankat!
Margo_oz is exactly right... the train is the way to go. It's only a ten-minute ride, and the station is right at the terminal (signs everywhere). You might have to change once to get a train to Circular Quay Station, but this is where you want to head... from the platform you can SEE the Opera House and the Harbour Bridge and the ferry wharves, so planning the next three hours will be easy!

Thanks so much for your help. Is is also possible to get to the Aquarium/Naval museum by this train?

If you want to go the the Sydney Axquarium, or the Maritime Museum, both are at Darling Harbour, not on the main harbour. Get off the train at Town Hall, and walk down the hill to Darling Harbour.

From Darling Harbour you can get a ferry around to Circular Quay and the main harbour (and vice versa), or you can walk - but it's a fair way. (or get the monorail back up the hill and then walk or get the train again!)