If you open the photoshop pages, you should be able to edit the graphics. The simplest way I can suggest that you start is not to move any of the graphics and simply replace them with ones exactly the same size that you have created. You don't need to edit your text here. Once you have changed a few images just to start; in photoshop click file save for web, and then images only. Save them to a folder that you can easily get to. Take the modified images and merge them with the original image folder that the template gave you.
Then when you upload the site into Dreamweaver (provided you haven't modified the size of any of these pictures) the site will still retain the same formatting and look. You can then edit your text from here.
If you need to adjust the size of the images, when in Photoshop, when you go to save for web you need to adjust the slice size of that particular image slice. You'll then have to change the picture size in dreamweaver and make it all fit together perfectly.
If I can be of any further assistance, please feel free to ask! Oh, and by the way I'm new on these forums as well!