Would be easier to setup a forum, and make a guest book thread. Make it where guests can post there, too. Easier upkeep, as it'll share one database, and just run off the forum resources.
Also helps to promote the forum, and draw traffic to it. Kind of a self-promotion.
If you need help in redesigning, I have all the time in the world for touchups. Even have vBulletin forumware I'm not even using (bought it more to keep up on design skills, not to host a community). Maybe Murray would be interested in getting under that hood, too. Just some options.