Use Velvia 50 at EI64. Take it to the max!
....or wuss out and use Provia 100. I don't think 400X has very nice colour, but more like an Edwardian looking-glass palette. You'd be wanting to accentuate the colours, which are sometimes pale and almost always fleeting. A long exposure will record more of the 'dancers in the dark' than a quick one, but it's all what strikes you as personal preference.
Northern lights and star trails would be a treat!!
By the reports I receive from correspondents in Oslo, you will come away with something, but not always a spectacular record of the lights. This year has been one of the best for 50 years, with I believe many shows of the relatively rare red/orange aurora layered with green. This is the apparently the exception, not the norm. Do lots of research to plot travel to expected aurora. The top north of the country is a hot spot for aurora-baggers.
I am heading to Norway in the next 3 years for the Northern Lights — research is proceeding. There are Norwegians here on APUG. It would be a great thread starter to discuss the aurora, travel options, timing and rubbing shoulders with Vikings...