Hi ya
If your looking at training it depends on where you want to be North or South island,Ful time ground school for cpl is about nine weeks i think ,and expect to pay between $400-450 hr all really depends on where you want to fly but even with 70 hours or so it will pretty much take you 6-7 months to get your cpl now that your heading into winter downunder.
Changing your Faa ppl should be to much of a problem prob just an air law exam and a flight test. Have a look at Nelson aviation college or Ardmore flight training for ground school start dates.Sorry been a while since i left N.Z but try having a look at training in N.Z on the search here.