Hi there Jeroen! I think I can answer a few of your questions, regarding the technical stuff.
- Silly question: do I need special tyres or are the ones that I use in the Alps sufficient?It's probably best to use winter tyres with studs, but its not recomended by law.
Where can I find maps of the region? (I already ordered "toppturer i Norge" );You should be able to buy detailed maps of the different regions, at any sportshop in Svolvær(city).
- Is there an avalanche service for the region that hands out daily snow bulletins?- What are the best weather sites ? (preferably in English) I would recommend; http://www.yr.no/ - They also give an avalanche forecast, which should give you some idea of the danger level -> And you get it in english.
It's nice to travel around in the winter time, and it is also very cheep ( by norwegian standards) to rent a cabin or find a place to park your camper.. IE this winter we had to pay about 500 kr per night for a 5 person cabin with kitchen and bathroom. And you will allways find something vacant.
Anyhow keep in mind that it is limited with daylight in Desember and January. Between 7. des and 6. jan. The sun doesn't rise. (but its still some daylight.)