all you need is a toolbar with toolbaritem for your menu and a contentcontrol where you set the content property to the content in dependence of your menu item. and if you do a little bit MVVM you simply set the vm to the content property and define some datatemplates for your views.
<Window>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Height="auto" />
<ColumnDefinition Height="*" />
</Grid.ColumnDefinitions>
<ToolBar Grid.Column="0">
</ToolBar>
<ContentControl Grid.Column="1" Content="{Binding Path=ActualWorkspace}" />
</Grid>
</Window>