Export a slice of the gradient to use as the tiled background image for the div you will be adding the search form to in Dreamweaver. Yoiu can't create the search form in Fireworks, nor can you easily add a gradient to the text box of a form.
Thanks for the reply. So you're saying just take a random slice somehwhere in the image and then make it repeat using CSS in my HTML? Should I include the borders in the slice or re-recreate the borders in CSS?
It would probably be easier to add the borders in CSS. If you do them with images, then you need to have a left and right edge, too. A CSS border property on the div is much easier and cleaner.
Here are some roundups of tutorials on styling forms:
http://www.smashingmagazine.com/2006/10/25/css-techniques-tutorials-layouts/ (scroll down to the form section)