Skin/Theme Development Help

I am trying to create two different “skins” for a site I am working on and it has to be user friendly for the client to go in and edit everything. I mocked the site in XHTML and have that working properly and now I am trying to put it in PHP to make the “skins” for my client. She wants the front page to have one look and feel and all the other interior pages to have a totally different look to them.

I am lost on what to do. Can anyone help me? Any suggestions would help.