Email to exclude discount group, etc

Question part one: Is it possible to send an email to all my customers except those in a particular discount group?

I want to send a coupon for a particular product category to all my customers, except those who already bought it. Everyone who bought it is in a discount group already, so this would be a good way to filter them out.

Question part two: Is there a way to automatically put new customers in a discount group? Or better yet, all those who purchase a particular product/category in a discount group automatically?

Question part three: Is there a way to assign someone multiple discount groups at the same time, or is it a one shot deal?

Thanks in advance. I can't figure this one out. :frusty: