Is OOL-SYD the start of a sequence of flights - i.e. do you move on from SYD within 24hrs? It's possible the change has an impact on all those flights.

I believe flights ex-NZ (including connecting flights) cannot be hit by fuel surcharges so you might have just lost that saving, though I thought that only applied to tickets originating in NZ which yours doesn't.

You might be able to price up the old/new trip on matrix.itasoftware.com and view the fees there but if you have a lot of legs it may require some fiddling. Care to post the full rtw (including stops >/<24hrs)?