If you aren't tech savvy, I would highly recommend shopify. It's designed with users like you in mind with a very simple back end that can run shipping, adding products and everything else you've mentioned. If you can run a wordpress site, you can run shopify.

After setting up my first store I was able to get the next one up in only a few hours. It's that easy. Also a great community for support as well as an impressive app developer community with new features coming out all the time.