The normal Google Analytic E-commerce Tracking that will save your time. Thanks to http://www.notesonclick.com/blog/add-google-analytics-e-commerce-tracking-in-opencart/
i've modified it into vqmod. Just paste the xml file into your vqmod. that's it for installation.
* i make this extension available for free to contribute back to the open source community. if you appreciate my work https://paypal.me/sapienstech