Right, PHP is a server-side language so you won't be able to "preview" it on your local machine unless you're running a web server that can parse PHP (such as Apache).
If you DO want to take this one step further, you can download and install a LAMP (Linux, Apache, MySQL, PHP) application such as
XAMPP and you'll be able to preview the website in your browser.
[ Just know that you won't need MySQL (that's for databases) -- it just comes with the package, so don't be scared
. ] Anyway, once that's working, you could even set up Dreamweaver to use a "testing server" which would also let you preview your pages in the "Preview" tab (as opposed to just testing it in your own browser).
I didn't suggest this initially as it would only complicate things further, and you mentioned you were looking for a simple solution. But if you're willing to use PHP to begin with, why not try? If you're trying to achieve more advanced things that HTML just can't do, it's the next step up.
Otherwise, your alternative method would be to simply make your changes, upload them to Lunarpages, and test it live (this is generally not a great idea, though).