Camera etc is your choice but I would recommend a lens around 20mm (on FF) with a fast aperture (2.8 minimum) for aurora images. Ideally 4 to 6 seconds is right for such images.
I’ve spent quite a bit of time in Iceland over the last couple of years, had a month there over the summer travelling around in a campervan, and each trip has been unique and special, it’s a fabulous place.