Some info about NZ roads-

They are mostly chip seal so see if you can get a carbon or steel bike and purchase well padded gloves.

Make sure whatever tyres you have are REALLY bullets proof and tell the organisers that you will need a few spare tyres- the chip seal and glass on the roads slahes your tyres up big time.

Buy and use a rear mirror- there are large trucks (milk tankers for instance) on small country roads you need to watch for.

There are big hills to climb and wind is a factor, so make sure some of your training includes these.

Also be aware that there's a huge debate happening at the moment (and it doesn't look like it's going away) about cyclists being on roads. There is a LOT of NZ drivers that are not pro cycling. Ride with caution.

Have fun and enjoy the scenery- I love cycling in NZ.