LKinnon,
Allow me to offer some advice; been in and out of country since Independence. There is good qualified information from long time PNG flight crew; I'll throw in my two 'bob's worth.......
AVGAS: Regardless of any arrangements made, the supply is still unreliable. Check the date of expiry on any drum fuel. The fuel will be mega expensive.
RADIO's: All aircraft entering PNG are required to carry HF radio and certain minimum number of mandatory frequencies. Depending on the type of HF radio fitted to your aircraft, the appropriate 'crystals' may have to be made. A synthesised HF is best.
NAVIGATION: Over the past few months virtually all remaining government operated Nav-Aids have been shut down. Exceptions would be ILS/DME at Port Moresby, and VOR/DME at Nadzab. Privately owned Nav-Aids continue to operate.
GPR RNAV: Totally new procedures are in place and will commence in early September. Some of the new published charts are available as in AIRAC 03/2019. Not all the charts have been issued to date.
MAINTENANCE: Not really available, due licencing inconsistencies between Australia and PNG
WEATHER: Forecasts and TAF's are unreliable.
IFR FLIGHT: Never descend below LSALT unless you are Visual, and I mean visual!
SAR: There is NO real SAR in country. In an emergency Operators tend to band together and pool resources.
WEAPONS: Don't carry any weapons as in Guns. Pulling the trigger is a lot different to just pointing the said gun.
MONEY: Don't carry money, you will be held up and robbed. Use credit cards,
I might suggest that if you don't have any real need to visit PNG, but you want to do so, fly PX of QF to Port Moresby and watch the 'fun' from there.
MOBILES: The PNG network with the best coverage is Digicel... Use a cheap phone something you can afford to loose if held up, same with your watch and camera's. Don't draw attention to yourself.
CHARTS: All the Maps and Charts in electronic format on Oz-Runways are grossly out of date, and it would be unwise to use any of the charts. (Approach/Enroute/) etc