3 column nested masterpage

I want to be able to have a third column nested master page which include the following in a box:

1) Recently viewed items
2) New Arrivals
or
3) Popular Items

Can anyone give me some leads into how I can do that?

Thanks

Hi,

Well create a new master page that inherits from the root master page and paste in the following code:

    <div id="container" style="width: 700px; overflow: auto; height: 1%">
        <div id="left" style="float: left; width: 200px; background: #f00; margin-right: 10px;">
            <p>
                left navigation column</p>
        </div>
        <div id="center" style="float: left; width: 300px; background: #0f0; margin-right: 10px;">
            <p>
                main column</p>
        </div>
        <div id="right" style="float: right; width: 180px; background: #00f;">
            <p>
                right navigation column</p>
        </div>
    </div>

in the left and right add you user controls for navigation and so on and on the center column add a content place holder and modify the rest of the pages to use this master page.

I am creating my first nop theme and I have 3 questions on master pages.
1) Is it better to update existing master pages, or is it better to add new master pages.
2) What will happen with theses master pages when I will apply nop update?
3) What is the best way to switch from one master page to another, because I cannot find a way to do this in tha admin options, like templates.

Thanks for your help!

Nicolas