How to find a truck mechanic while traveling in New Zealand

We are traveling through New Zealand for 8 months and bought a Motorhome that is built onto a 1994 Ford Trader Diesel truck.

We are on our way to the South island and appear to have an oil leak and want to get it fixed before we cross over.

How does one go about finding a good mechanic in Wellington?

There is Yelp and TripAdvisor for typical traveling searches, how would a kiwi find good services?

We have never owned a truck before and google searches don't appear to be helping.

There are some sites: localist, nocowboys, trademe but it is hard to know if they are for real or not.