you mentioned that you were completely illiterate in this area.If you have never used or installed scripts before or have never made a website, there is alot to learn. Yes there are several scripts that are free that can be used for an ecommerce website. I can recommend a few as well, but that doesnt help you if you have no skills in actually starting a site. Here is my advice. Find a free cpanel host that has "1 click script installs" (usually called fantastico or scriptaculous) once in cpanel you can find the 1 click script install software, and install scripts such as opencart, and prestashop to name a few. (long list here http://www.softaculous.com/softaculous/apps/ecommerce) Once you installed one, try it. Odds are you wont have the skills to customize the theme, so if you dont like the look and feel, and if there isnt other themes to switch to, you can just erase it and try something else.Or install several, and setup a few fake products and see which one that you find the best to use for you. I am only recommending to use a free host so that you can try it without it costing you. Once you decide on which software to use, of course, join a solid reliable host. I hope my advice actually helps you, not to choose the software, but in how to get started with installing it to try them out for yourself.
Go to www.Worldconnectwebdesign.com/ they will help you with EVERYTHING... logo, content, banner ads ect... They are wonderful and helpful
I personally used magento & I think its hard to customize it, if you are not a technical person OR you don't have professional person who could handle technical stuff for you then don't go for Magento Wordpress is good but though you also need to customize it and I believe customizing wordpress is easy than magento
Why don't you order something from some Web-designer... IMO, if you don't have experience, you'll lose to much time until you learn... just my two cents.