with all my luggage
if you have a lot, then flying to Warsaw and then catching a connecting flight to Goleniow/Szczecin would be your best option, because you are flying from NZ, which would probably take you hours resulting in being tired and less alert.
If you have only few suitcases, then flying to Berlin is a good option, from where you can catch a 2 hour train ride to Szczecin, or better yet, get a ride in a private minibus run by Poles doing the Berlin -Szczecin route (1,5 hour ride) on a daily basis.