You are permitted to drive on a full UK licence in NZ for 12 months. To get a Kiwi licence, all you need to do is take a theory test (just a scratchcard test with 30 questions) and an eyesight test. I would recommend taking the theory test well before your 12 months is up, just in case you fail, gives you a chance to swot up and retake it - if your 12 months expires and you still don't have a Kiwi licence, you won't be able to drive!
HTH
