Nissan Sunnys weren't produced after 2006, so your car must have been between 12 years and 46 years old. I never knew cars to last that long in PNG, should have been in a museum!
Around 1963 or 1964 I had a '57 Holden FE sedan in Port Moresby. The Haus Boi, a Goilala often watched me cleaning the car and one day asked me if he could clean it. That should have set the alarm bells off in any Expat, but no, I told him to go ahead.
Using the garden hose, he did a great job removing all the dust from behind the dash board, under the seats and washed the carpets in situ.
Took days of drying out to get it running again. The bench seats had cloth inserts and every time I sat in the car for months I got wet to the skin. Never did get the smell of mould out of the car!