sofasurfer:
Is there a source of documentation that will help me with this?
There is no single source of instruction about styling or configuring Zencart. You have the Tutorials/FAQ (link above) and this forum.
The best advice I can offer is to install Zencart in a subdirectory of your domain.and consider it a test site you'll use to learn how everything works. Then, when you know more, install Zencart again for your live site.
You'll need these tools:
An FTP program - many here use Filezilla'
A good text editor. I use Notepad ++.
Then install the Firefox browser and the Web Developer plugin for Firefox. You can use those to see where in the stylesheet you change the styling of the various page elements.
Ctrl-Shift-Y will allow you to hover over a section of the page and see the class and id names for that section in the box at the top. The statements in the stylesheet that begin with # are id's and the ones that begin with dots are classes.
Ctrl-Shift-E will open the CSS editor and allow you to edit the stylesheet and see the changes in real time without changing anything permanently. An essential tool.
(If you're using Firefox 4, you'll need to remap the keybord shortcut for the editor - FF has taken over Ctrl-Shift-E for something else.)
Some prefer Firebug, which does much the same thing.