congrats!

1. 17 miles is a long way for anyone unless you're Lance.
2. Yes, it can be quite dark. Personally, I would recommend a sub-20 dollar light set off of amazon until you're sure what you want (i wouldn't make huge investments initially ... you need to ride and see what you like first.
3. that's normal. it will get better after a week or so. you can go with padded shorts (but again i'd wait and commute for a few weeks before buying an cycle-specific clothing)
4.