Just in case you are tempted by Artisteer... My advice is don't bother- a co-developer friend of mine paid for this software and its capabilities are modest and the results are not so great in my opinion.
If you are not an artist/designer then you will get much better results adapting an existing theme. You can start by putting together a shortlist of free themes you like. The next step is to discern which themes on your list have good levels of support, and many do? Visiting the designer's site/forum you can often get help to customize elements for a unique look. Using FireBug makes it easy to identify elements, and with a few changes you can customize most themes.
I'd also recommend you consider Drupal for your website. Drupal is felt by some to be harder than WordPress, though you can keep things as simple as you like. The advantage of Drupal is it is far more powerful and many of the free themes are extremely well supported. Without any coding experience it took me about 10 days to create a custom (adapted) themed site with full shopping cart and including product video slideshows, in drupal.
