If you have an existing Search and results page, then you can add the search to an existing recordset by applying the DataAssist Search server behavior on the results page.
Once you find the layout that is closest to the one you want you can create those pages with the wizard. Once the wizard has run you should make all changes moving forward from Dreamweaver outside of the wizard.
Yes, you can place add to cart buttons on the results and details pages.
The pages will be positioned within the theme or can be plugged into an existing template. If and how they react depends on the css and html layout you are using.