If bikes are like walking gear, then it will be scrub everything to within an inch of its life before you get there, possibly followed by them scrubbing it all again for you, possibly for a fee. More to the point, same on your way back to Oz, then possibly again into TAS depending on what quarantine officers they have at the airport. Consequently, when I went to chch a couple of years back, I just hired to save the hassle (though you still need to clean all your gear etc).
Visas, if you have PR in Oz you should get PR in NZ until you leave (i.e. residency is lost after you leave, so presumably you just re-apply by presenting your Oz PR visa next time you go) – just watch which queue to go through at immigration. I was in the bizarre situation of having PR whilst I was there through having PR in Oz, yet the mate I was visiting was facing being booted out in a few weeks as he only had a temporary visa. I assume I just get another PR stamp next time I go…