Adding post descriptions to category pages

Using WordPress 2.1, here’s what I’m trying to do:

1. Publish a post to a selected category (easy)
2. Have post automatically listed on the category page (easy)
3. Have a “sticky intro” at the top of the category page (don’t know how)
4. Display a POST DESCRIPTION (or a 2-line excerpt from the post), rather than just a list of titles or the entire freakin’ post, for each post in that category list.

Is there a plug-in I can install that will let me do this, or some code I can modify? Go easy on the techno-speak, I’m a designer, not a coder. Here’s a text-only example of how I’d like the page to end up (or something close to this):
—————————–

Category Page Title

This is a welcome message that stays at the top all the time, explaining the page to new visitors. The rest of the page will be descending chronological summary of posts in this category, that looks a little bit like this:

[horizontal divide]
Linked post title * Date
# Comments * Posted in Category by Author
Brief description of what this post is about, or a two-line excerpt from the post itself. Brief description of what this post is about, or…
[horizontal divide]

[another box just like above]

—————————–

Does anybody have any ideas? Any help would be appreciated.