Hi Rob

Easy answers, yes, yes and probably.

You can pick up a sim card at any retail store or walking through the airport.  Vodafone and Telecom have micro sim packs and then you guy load them up.

There's set up details on the Vodafone plan, but anyone in any store should be able to help you out.

Vodafone

https://www.vodafone.co.nz/ipad/ipad-plans.jsp - Vodafone Plans

Telecom

http://store.telecom.co.nz/mob…..osim-offer - Telecom Sim Special Offer

http://www.telecom.co.nz/mobil…..ng/prepaid - Telecom Plans

2 Degrees

http://www.2degreesmobile.co.n…..data-packs

http://www.2degreesmobile.co.nz/ipad

2 Degrees, I'm not sure about, I've heard some people having problems getting micro-sims in store.

I'm on Vodafone and find it great, There's decent national coverage for the 2 majors Vodafone and Telecom.  I'll let some of my Southern brethren comment on network coverage in the South. 

Set up should be easy, you might just need to put the sim card in and you follow the instructions, as long as the Carrier option in your settings it automatic it should find your chosen network.

You can top up your Vodafone sim card by purchasing a top up at store, so no need for a credit card, it's very relaxed here for prepaid.

Enjoy your trip

no worries Rob.

Have a look at http://www.tourismradio.co.nz, it's a service outlining points of interest on your travels, for $40.00NZ.

Have fun here.

A point to note: the 1st generation iPad does not support the 'rural' or extended 3G frequency that vodafone uses.
The frequency (850 MHz) that Telecom 3G is on nationwide is supported by iPad 1.
You should request telecom to set up your prepaid sim with the 500meg data add-on, available by ringing *333 from a phone with the sim in. Data will then cost you 10c per MB. Tell them what you want, not all telecom sales reps seem to know the 500 meg add-on is available