We went to New Zealand last year, primarily the South Island (which is prettiest) and then visited friends in Wellington before flying home. There are direct non-stop 747 flights that go to either Aukland or Christchurch from CA, some roundtrip fares for just over $700 right now. Christchurch is a great area to fly into, unless you're going to stay in Aukland, because it's a smaller airport and can get fogged in for connecting flights quite often. 747s land there, however. It is a much easier checkin for international flights. Interesting that there is virtually no security procedure in NZ, you just whisk right through.
Our trip was fabulous and I kept a travel journal of all the spots we visited and the places we stayed and dined. I read about a dozen travel books on NZ and also relied on my husband's knowledge of the area before our trip. The most amazing thing was how obviously NZ is a cross between the Antarctic region (which it separated from geographically) and a tropical climate. On one island, you would get penguins and glaciers and also have wild orchids growing in tropical rain forests and beautiful sunny beaches. The people are perhaps the most friendly and hospitable we've come across in all our travels. And the food and wines are wonderful. Everything is casual there.
Some must see spots: Christchurch, the Southern Peninsula, Doubtful Sound daytrip on the boats (it is by far the preferable of the two Sound trips), the Antarctic Museum (a little corny, but very informative and the ride is fun), Moeraki Boulders, Queenstown and (better yet) the nearby historic mining town of Arrowtown (many good wineries with their own restaurants in this area; do NOT stay in Queenstown proper because it is far too touristy and too much construction going on in a cramped area), the Tasman Sea coastal area and National Park, Pancake Rocks, and the artist colony coastal and fishing town called Nelson. We took the ferry from the South Island to Wellington at the southern tip of the North Island, which is the home of Peter Jackson's film studios and where "King Kong" was largely filmed. If you go to Wellington, be sure to visit The Te Papa Natural Historic Museum, which offers interactive experiences and a great history of the native Maoris.
If you would like a copy of my travel journal via e-mail, send me a PM with yours. If you would like to have it with the color photos, send me a mailing address and I'm happy to share it with you. You will not regret making this trip, one of our best yet anywhere in the world. And FYI, getting an upgrade on these flights is next to impossible because so many are willing to pay the considerable price due to length of trip. However, we found Air New Zealand much roomier than our domestic airlines, the service far superior, and we were quite comfy sleeping the night in coach. It is much easier to lose an entire day in crossing the international date line than to lose part of a day as one does traveling to European countries. We took an early evening flight, had a light dinner, popped an Ambien, and woke up totally refreshed in time for the breakfast service. Then just resumed our usual schedule upon arrival.
Bon voyage!