1. adverb.
If you have to choose one, choose adverb. In this sentence around is telling you where my friends and I looked. It is modifying looked so it is an adverb.
2. adverb
Same reasoning as number 1. Usually before is a preposition, but in this sentence it is an adverb because it tells when they had never been sledding. A word that answer when like today, yesterday, tomorrow are adverbs.
3. into
4. at
5. in
Preposition tell the relation of one noun to another. These words all give you some indication of the relationship between the subject of the sentence and another noun (history, St. Joseph, days).