Magento(ecommerce form)/Marketo Form

Hi,

I wanted to know what options we had for tracking our ecommerce orders in the same way as we do a marketo capture form.

As it stands we use magento forms for the checkout process on our store/ecommerce site e.g store.bmiresearch.com - as this also involves creating a new user and an account in magento, and is pushed as an order to salesforce this cannot be replaced. 

The piece I am missing however is tracking any new users as I would through a standard marketo form - i.e tracking the cookie on the user to see web activity, plus capture all the original source details so I am able to capture original medium e.g email, ppc etc?

What options do I have here?

Thanks