Sounds utterly fantastic.
My tip is not to come home again and try to look out of the windscreen when driving rather than dribbling down the window, looking at the views.
You'll have so much to see up there, what an amazing drive.
You can buy good quality kit in Kiruna at the hunting shop. It's very well stocked and the guys in the shop know their stuff. Abisko and the Tornetrask valley are 30 miles from Kiruna, very well worth visiting and spending a couple of days at least. It has the blue hole of Abisko for aurora viewing and the iconic Lapporten, an ancient Saami campground with a very special feel to the place to me.
I've not yet been to the north cape and Kirkenes area but will do before long. I won't bore you with Varanger and Tromso as you've obviously looked at those. Places that are on the list up there for me are the Pasvik valley near Kirkeness, Stabbursdalen near Alta. Central Finnmark is proper Sami country with softer looking land and rounded hills. It doesn't have the shapely mountains of lots of the rest of Norway. Its by far the coldest part though, hits -50c on the plateau in places and the temp forecasts can be unreliable there (ie, forecast -8c, actually -39c for example).
This is the best Norwegian weather site;
http://www.yr.no/place/Norway/Finnmark/Karasjok/Karasjok~303806/
Norwegian winter trail map;
http://www.nordatlas.no/default.aspx?gui=1&lang=2
Kiruna is a good place to start from. Also worth looking at flying into Tromso as it's a direct flight. Ivalo in Finland too.