PNG has a few quirks. One is that there is no road connection between Pt Moresby and the rest of PNG.
The main road system from the NE coast up through the highlands is well served by a network of adhoc transportation conveyancers called PMVs. They come in three classes. Very uncomfortable, excruciatingly uncomfortable and life threatening. All the same price, and it just depends on how crowded it is as to which class you travel in.
If you are talking about doing it on a motorbike then you will need to be highly experienced at avoiding potholes, mud, pigs, kids and people. Likely result of hitting any of the last three is death.
Speaking of mud, this was in the dry season. --
If you can figure a way to install something like this on your bike
It might deflect a few of the rocks and machette swipes that tend to do a fair bit of damage to bones and tendons
Apart from that, its an interesting place. I enjoy it.
Mostly.
And when they are not hacking each other up over payback issues, they are very friendly
Oh and be very careful in Port Moresby and Mt Hagin. In either place, if you have a truck with goods on the back, you need one person on each corner to reduce the speed at which the whole load gets stolen. My first night in Mt hagin a gang of raskals attacked the motel my daughter and I were staying at and shot and slashed the place up pretty badly
Entry visa is available at the airport when you fly in to Jacksons at Port Moresby - for Australians anyway. Cost 100 kina. 60 days single entry and you MUST have an outwards ticket.