Take cotton underwear, not Damart. you need to wear several layers and also a pair of warm ski-pants will not come amiss when scootering ( cold knees) Believe me, I didn't want to wear them, but when I did, it was so much better.
Also, socks: wool and : or cotton. 2 or 3 pairs, plus the special boots you get along with the overalls. Nothing is worse than cold feet. Your own boots for evening walks shouls also be warm and water resistant.
Cold is dangerous!!
Get your gear from Club Nord at hotel Ivalo in Ivalo. ( Ivalo has only about 4000 inhabitants )
The only danger I could think of is to be careful when driving on the roads as there are plenty of Reindeers around. Especially when going further north close to Inari