Coming (back) to New Zealand

My wife and I are trying to figure out how to move from the US to NZ on a temporary retirement visitor visa. Retired doctor and (various), now mostly interested in nature studies as a way to be outdoors. We've studied the visa requirements and are trying to satisfy the requirements. This week's subjects of interest:

1. We have good health insurance to bring with us, but are struggling with finding dental coverage and evacuation/repatriation coverage to meet the requirements.
2. We're trying to come up with a strategy for finding an area to live in and a house to rent in that area. We will be visiting next month and spending a couple of days each in Hamilton, Napier, Wellington, Nelson, and Christchurch, but would love to meet a real estate agent in each area to show us or at least point us towards neighborhoods/areas that we should be looking at.
3. I'm strongly leaning towards hiring an immigration advisor to help us with the process but not sure if that is worth the expense or which company to go with.
4. Cell phone: We'd like to have a way for real estate agents and others to call us while we are visiting; what's the best way to do that? Is WhatsApp in widespread use? Get a SIM card or SIM card for one of our phones?

So many questions! Any suggestions very much appreciated.