we had theory lessons arranged through a driving school and went along to the classes - all the different possible test questions are given over a period of time. It's a matter of getting to grips with the specific driving language. So after class we'd look up all the words we didn't know (I jotted them down during the 'lesson') and it made such a difference to understanding the questions. btw - if you end up losing your licence through loss of points you must do this class anyway - so our classmates were either youngsters learning or those who had already lost their licence and going to the compulsory classes to regain it. Just before the test we had one practical lesson to explain what the examiners would say with their instructions and how to do certain things like crane your neck at an intersection to prove you've actually looked. The whole exercise was really useful. There was also an option for another written test for foreigners (they give the question twice and a bit longer to answer) but as that is only twice a year or so, our tutor said he had complete confidence that we could do it in french - and so we did :)
And yes, if we'd known about this before we left NZ, we would have taken a small side trip to Vanuatu and got a driving licence there which we could have simply exchanged for a French one.