I'd be curious if my answer to your question is correct.
I've been analyzing how php code is written and though I think it's set up very primitively (meaning there's no WYSIWYG option except for changing the code and then uploading and reviewing the change in real life). A php editor with a test viewing option would be very helpful I'm sure. I haven't looked around for MACS but I seem to remember seeing a program for PC's.
So without a WYSIWYG editor you have to move the coding around for your formatting.
To adjust the php code for the layout change you have to first understand how the code matches the layout. As far as I can see the way it's set up is using a set of rules for CSS layout with div styles written within the coding, and again I may be wrong as I'm a newbie in understanding php code.
Right now it's set up for 2 columns (float left, float right) but what you want is to create a single column that spans above the 2 columns across the container of the layout page. To create what you want you would have to first see if it's possible to have a main column above the 3 columns and since no one answered your question it's probably not possible. However I would research it and find out.
I know it's possible to shift around the blocks (price block, attributes blocks ets) on the page and the position of everything really on the page. You might have to create a new block for what you want above everything else. As I said I don't know php very fluently but am learning there are possibilities.
Get a php manual, that will also help.
Beth-Katherine, who has probably confused the whole issue