plz help

That depends on what your lifestyle is like, how much power you will use, how much food you consume, your telephony costs, internet...  US$3500 is a good income by local standards, how ever you will be taxed graduated up to 42%, plus you will be taxed on vehicle and accomodation.

thanks bro...i dont get it one thing,the company will provide the transportation and accomodation so i will stay at the accomodation that proivded and they will sent and pick me up every working days..do i have to pay for the taxed also??

Legally, yes - you will have to pay tax on accomodation - but not on the car.

Having a pickup/dropoff service for work, doesn't count as vehicle - however it also means you can't get out and about.  Port Moresby is not somewhere where you can just wander down the road, or jump in a bus like the locals, although both my father and myself do this (he does the PMV's - I don't).

On the bright side - if you are stuck in a compound, you won't spend any money - but you will have no life I'm afraid.

Is the company going to pay for medical, life, medivac insurance?

There are many PNG sites our there now, my biggest suggestion would be to really research PNG before committing yourself.

Any suggestion PNG site that i can search?

Look at this post on my blog

http://kiwiexpat.wordpress.com/2011/07/09/png-bloggers/

thank you...very useful guide.

If your package includes accommodation then that is pretty good.  You could live quite well on that amount I think.