I usually do the custom coding thing myself to have finer control, but if I recall, there is a plugin named "Category Page" (http://wordpress.org/extend/plugins/page2cat/) that allows you to assign a "page" to the head of a category. Maybe there are some functions you can siphon off to get what you need?
It may even provide some functionality that allows you to write a full page, use shortcodes to cycle through your posts, then add more content below.
Disclaimer: I am not associated with the plugin, and I haven't used it in a long time. Do your own diligence.