What are you talking about you cant do it in one go?
Catch the last bluebridge ferry the 230am one, they now have cabins for $25 have a shower and a sleep and continue on..
Leave after 12pm, this will allow a 1hr food stop, in Taupo or Palmy.
Arrive in Wellington, refill your petrol! grab some supplies, water food etc.
Check in and line up early as its first on first off.
Have a nap in the car, grab a cabin and have a shower, go to sleep!
Dont worry about sleeping in as they bang on all the doors and get you up.
Get off the ferry and pass as many cars as possible so you Dont get stuck behind trucks or camper vans going up the hill.
Stop for breakfast in Kaikoura
Youll be home before lunch.
Have driven and done this a few times, but to Dunedin.
Nothing to look out for, just check your tyre pressure, Youll need to put in more psi if you are loading the car up.
Lots of tunes, i usually drive fast as it keeps you more alert.. Well me anyway.
Always drive the posted limit through towns.