I created a website selling Wix filters
www.fleetfilter.com about three years ago, and I did so with minimal investment ($600). To get started, I used Google's Merchant Svcs stuff because the site was easy to create, easy to host, and mainly because they had a built-in shopping cart. When sales justified the change, I went to a pro and had a full website built with normal shopping cart abilities. Apparently, there are a few companies out there who build the shopping cart side of the site and you just have to put their code on your pages (you pay for the code), but as a non-website-engineer, it sure seemed like it was way over my head to have that done properly by myself. Not to mention, I had no idea which companies made good shopping carts and which ones made crappy carts.
Which means, you're either stuck with Google's shopping cart (or similar), or you'll need to find someone who's created shopping carts before on websites and have him build the pages with the code. Since your site is just getting started, I'd recommend you start using Google or something like that - it's easy, efficient, and when done properly, it can look pretty good.