MVVM-Light/WPF Navigation Application

As I write a WPF application with MVVM Light, I'm trying to determine the best way to allow for Navigation in the application. I've been reading about creating Services, Interf开发者_如何学Goaces, and Helpers, but unfortunately my head still hasn't grasped the great advice being offered on SO. I got down a spiral of starting with a simple class and some code behind to use MEF and/or Unity to accomplish my task.

What do you find to be the simplest way to add basic Navigation of a frame to an MVVM Light application built on WPF?

The problem seems light, but it's hard. The solution must cover several aspects as navigating to an existing view, closing a view, injecting the viewmodel before navigating to the view, animated transitions, etc.

A simple navigation mvvm-light navigation demo. https://bitbucket.org/dbeattie/navdemo/src