Welcome to the board.
1. I have a thread called "Power to the iPod" where I discuss one way to power your iPod with the cable you bought. Do a search and you'll find it.
2. I believe they are called Turbo Twists. They look chromed.
3. Yes, all Boxsters have this spoiler. Depending on your model year you'll have a switch down near the fusebox. If you want you can use that to put your spoiler up and down.
Other than that there's no easy way to see its up unless you can see your shadow on the road. I'm sure tall dudes can turn around to see it, but I can't.