Web Design editing with fireworks

hello,

I only own Fireworks and Dreamweaver 8. Most of the stuff I read on here is how to use photoshop. I was wondering if anyone can help me with how to edit the pages in fireworks. I can edit the images individually to change the site, but that is an impossibility in some circumstances. (such as where roll over images are). How can I make changes to the psd document and save it and have it reproduce the images in the /image folder. I've tried making changes and then exporting, but them it just makes a giant image. What do I do?

Thanks