You might want to try out some of the many mvvm frameworks out there. I personally like mvvm light because it works in silverlight and WPF, and it's easy to use http://mvvmlight.codeplex.com/ (no affiliation)
Here is a nice compare/contrast of some of the major frameworks: What framework for MVVM should I use?
Most of the frameworks have a messaging system that provides the ability to send updates between the view and the viewmodel as well as between viewmodels. Most of the frameworks also provide canned messages that handle MVVM messageboxs as well (I know MVVM Light does).
To handle switching between views in WPF I use DataTemplates and Content controls
In the view .xaml I add
<ContentControl Content="{Binding ActiveViewModel}" />
and this is the space where the injected view will be displayed. The ActiveViewModel is the object for the viewModel that holds the selected viewModel.
In a ResourceDictionary I add something like:
<DataTemplate DataType="{x:Type ViewModelNameSpace:ViewModelClassName}">
<ViewNameSpace:ViewClasName/>
</DataTemplate>
Finally in the ViewModel I set the ActiveViewModel property (that is setup to notify the UI of changes via INotifyPropertyChanged) to an instance of the viewModel I would like to use.
ActiveViewModel = new ViewModelClass();