From Sydney to Great Barriers Reef

Hi,

Has anyone gone from Sydney to Great Barrier Reef yet?
My question is what is the best trip option (should we fly to Cairns from Sydney and then take a day trip to the Reefs from Cairns?)

Is 2 days enough or should we stay more?
Is there anything to checkout in Cairns as well?

What accommodation options I have? (I assume we should sleep in Cairns...)

any tips and advice would be much appreciated

Thanks
Laleh