Yes, setting page-width to 100% works for wide-screen too. Whether you use percentage or fixed widths for the other divs is up to you - it depends on what you want the page to look like.
For instance, a left-column is often used for a vertical sub-menu and perhaps some information or advertising boxes, so as these would most likely be fixed widths themselves, you would probably want that column to be a fixed width (not a percentage of the total).
You may want the header and footer to be 100% widths, but have the content area a fixed width and centred. The best thing would be to try various different layouts using CSS Sculptor just to see what you can do with it.
