That mission is everywhere, but there is an importance in giving priority to overseas mission. There are many reasons to say that but here are two:
1st - the ratio of numbers of those who know Jesus to those who don't is much lower in New Zealand than in most countries around the world.
2nd - is our Christian heritage. From that heritage the world has received so much well-being, especially in the areas of health, education and justice. These were spread around the world by the church more than any other agency.
New Zealand's first public schools came with the missionaries settled here by Marsden in 1814. We don't have a monopoly on any of the great benefits spread by the church. Nor are we squeaky clean in regard to any of them. However the God we proclaim is good, and hasn't given up on us.
For the 2,000 years of the history of the church, as people come to faith in Jesus, something happens in them. John Wesley noticed it in the revivals he saw. He called it "Redemption and lift".
It's well said, if you had the cure for the worse disease on earth, you would want to get it out there for all to share. The worst condition there is affects every one of us. It's called sin. There is one cure - and only one. It's the forgiveness and redemption that Jesus brings. 
Now what is required is for those of us who claim to follow him to be more aware of the treasure we have, to support those who go from here, and we ourselves to share in word and deed wherever we are - here or away.

This month at Nativity we are having a focus on overseas missions. For many years some people have challenged my support for making overseas mission a priority, though I hasten to add, I haven't had that at Nativity.
"Surely" people say "we have more than enough needs right here in our own backyard." 
Is that a valid challenge?
My reasoning for my stance is simple. It's based on when I was the newly ordained Curate (assistant priest) in Hawera. 
I wanted to do some Parish visiting in the isolated back country behind Ararata. So headed off into the hills first thing and started visiting. By the end of each day I had made some good visits, but not made much ground.
One week I changed tactics. I travelled to the far end of the valley and worked my way back. People who'd not had a visitor in decades were delighted. Several made the effort to come to worship. Others were simply encouraged that someone from town was thinking of them.
But what I also found was those who lived close to town had visits or contact anyway.
So when it comes to our mission I believe it's the same one, be it here or there. Yes it's rightly done differently in different contexts. But if we don't start at the distant point, we'll never get there. In the meantime those closer will probably get what they need anyway.