As Izabella says, "set the camera settings up BEFORE you expect the lights." - for one thing, it will (obviously) be dark when you see the lights, and you don't want to be fiddling with settings in the dark and trying to actually SEE the merry dancers as well as photograph them. It could be very cold, too, and your fingers won't be so nimble.
I did a Google search with Northern Lights photography nikon and a whole lot of web pages came up with helpful advice.
It would be a good idea to try a few practice runs beforehand of night shots that include dimly lit clouds or some such thing, to get some experience of handling the camera in similar conditions.
God luck. When I went to Iceland, the only night the lights appeared the weather was so bad that the planned trip out away from street lights had to be cancelled.
