dave
Dreamweaver will not help you very much to see your changes on the .tpl files - you will have to either have confidence in your coding and post the change and then view the site.
You can alway open DW and create a html page and put the tpl code into that to see it in design mode - obviously there are some cart codes that may not work correctly but this will at least let you see something visually.
You have to remember that there are tons of .tpl files that make up the page and therefore to see something visually is very hard to do.
good luck