I agree. Both Zen and Oscommerce would be a good place for you to start with your store. Keep in mind that these will only get your site up and running. Once the site is made, you will then be tasked with getting your site to rank in the search engines.
Since you are new to ecommerce, I recommend reading as much as you can in this and other ebusiness forums. Also check out these website for some more good information.
Entrepreneur -
http://www.entrepreneur.com/
Yahoo Small Business -
http://smallbusiness.yahoo.com
Clickz -
http://clickz.com
AllBusiness -
http://www.allbusiness.com/