Take a look at the core of what you need to know here:
I answered these questions for those starting their own eCommerce store, and that is a great resource for you to get going! Feel free to reach out to me directly for more tips, we can set up a call.
A good question would be on the framework to see if they ever opened the code or just used it as is:
Magento is based on Zend Framework and MVC development.
Late to game here but Matt from Demac media in toronto is one savvy magneto eCommerce guy...reach out