We did this earlier this year and that info is correct. 2.5 hours is more than enough time for the connection, so you will have a good margin if the flight is late (as they routinely are).

You won't go through passport control or customs in SYD, though you will have another security screening (but the line should be pretty quick). Unfortunately it was a long hike from the UA gate back to the security screening (and then for us another long hike back to the departure area) but that was really the only hassle.

Be sure to check out the NZ lounge (you will have access with your C tix) it is quite wonderful and well stocked with food and beverages

P.S. How did you get two C saver awards on the SYD flight (i.e. how far in advance, for what month)? I never see any available on .bomb