eCart does not currently directly support Google Checkout. If you are familiar with implementing Google Checkout by hand, then it would be easy to implement eCart, but it is a relatively complex system.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.