Using Thumbnails in the BP Magazine Theme

Hi guys

A couple of questions about thumbnails:

- If I have several pictures within my post, how do I choose which one is used as the thumb?
- Can I designate a picture for a thumbnail that isn't actually featured within the post itself?
Also:
- Can I control the amount of post text that is brought back on the front page?
- Can I change the text that overlays the thumb (currently it uses the post date)?

Thanks!

Jason