Grow kits and spores

If I buy a mushroom growkit, how difficult is the process from Syringe to kit?

I've been looking at grow kits online on dutch websites that I've purchased truffles from before (successfully) and they send to NZ ready to just be watered and bagged, but obviously there's a big risk in them getting through customs.

Can anybody help me out with this dilemma? Many pleases and more thank yous.