To create a preview  page some thing that comes to my mind is to:
Identify the pieces that end user wont see in the Final published  page, for e.g.: Site Actions menu, Left navigation bar, Publishing tool bar, etc.

Once you have identified the pieces, you can create a CSS file to hide all these elements (as the elements will be wrapped in some or the other CSS class and you can simply set the Display = none for these css classes in your custom CSS file). This way you can render the page as the end user would see it.

Something that is easily done for Print Prview kind of output:
panvega.wordpress.com/.../