Forum Moderators: phranque
I would install a rich textarea editor such as TinyMCE (my favorite), SPAW, FKedit (FCKedit?), HTMLArea, Bitflux editor, or any of several commercial ones that don't cost a lot (but this doesn't sound like a big budget project.
Then just put the main page area into a form and read and write it to a text file that gets included in the page.
(I have a feeling I'm going to kick myself when I hear the answer!)
You need to familiarise yourself with php basics before you get started, but an approach you could take would be to update the required content in a textfile via a form and then include that file in the php page.