I have been getting a lot of requests to make ecommerce sections to sites and I wanted to know if there are any tutorials online describing how to get started, I understand that it can be a difficult system due to security and function, but I wanted to get some basics so I can understand it.

I have also seen some packages and services that say they can be customized to blend in seamlessly with your site I am thinking they might be a better choice than trying to program these things from scratch.

Anyone have any tutorials or input on going from scratch vs. template.