Setting up Google Tag Manager / Google Analytics with Commerce7.

At Commerce7 we have Google Tag Manager installed throughout the platform. We follow the Enhanced Ecommerce verbatim as Google specifies (except we don't handle refunds). This is great if you want to embed Facebook Tracking Pixels or any number of GTM like scripts on a site.  
GTM can be used to connect with GA. Several of our partners offer a service to take GTM to GA. They access your GA account and then import all the GTM code we have and set everything up. Contact support@commerce7.com to learn about your partner options.

Note: Using a partner option is additional fee. You can contact the partner you choose for exact pricing.

 
Setting Up GTM:
To set it up - in WordPress you will need to add the GTM containers to the head and body tags.  https://developers.google.com/tag-manager/quickstart
We felt doing this in WordPress would give you the most control.
There is nothing to configure on Commerce7.
 
Enhanced Ecommerce:
We implemented the Enhanced Ecommerce from https://developers.google.com/tag-manager/enhanced-ecommerce - and we did it on the window.dataLayer (as opposed to a custom data layer).  
We followed this documentation explicitly except that we didn't implement refunds and promotion impressions.  You will get product impressions, clicks, checkout steps, etc.