Nope, not enough time so I would be phoning to have an earlier Syd>BNE flight if I was you.

Im guessing as its the same PNR, your luggage will be checked through from Sydney to LAX.

When you land at BNE domestic, you have to take either the airtrain (across road from terminal) or bus (outside terminal) to International. Ive taken the airtrain and thought waiting around the terminal was a bit of a waste so would take the bus next time. I believe your transfer is free with QANTAS.

Once at International, you have to go through security and then immigration.

If you are unlucky enough to be travelling during school holidays - its VERY busy (as I learnt in April).