I'm not going June 20; I took the Australia, NZ, Fiji trip a couple of years ago and loved it. It is very busy and I thought ending the trip in Fiji was wonderful, so relaxing after a lot of road travel. It's likely that other June 20 participants aren't reading the forum.
For tips, have you read the traveler reviews of the trip? Have you done a search under
"Destinations" then "South Pacific?" There have been several threads on this trip so you might find answers to your questions there.
You're in for a great adventure.