I don't think you can achieve exactly what you described. The instance needs the disk while it is running. After it shuts down you can delete the disk.
Google compute engine exposes REST API. You can issue the calls to delete disk and remove instance from some other machine (i.e. your work machine). If you want to, you can even use AppEngine to help you with this. An instance could put a task onto the task queue before it shuts down, and the AppEngine task, which would run a bit later could properly clean up the GCE instance. You could also use AppEngine to run a small admin application which could help you with managing your GCE instances.