Really you don't need anything but Dreamweaver to do a guestbook. All you need is the basic DW insert form set up with PHP and MySQL (You would need to have that set up even if you used a plugin)
Generally when I do a quest book, I set up my fields in my Database and create an Input form to have users add the record to the database. Then have a 'View Guestbook' page that displays the guestbook data from the database.
By using the WebAssist Data Assist product you can even do more advanced stuff like having to approve the guest book entry before its shown etc very very easily. Maybe I might have to write a tutorial for a simple guestbook with only Dreamweaver? ;-)
Adobe Community Professional: Dreamweaver
Northern British Columbia Adobe Usergroup: Manager
Thompson Rivers University: Dreamweaver Instructor
My Adobe Blog: blog.lawryk.com