I haven't tried this myself, but the WP framework has the Window.Current.Content
object which you can use to load different views.
For example:
// Create a Frame to act navigation context and navigate to the first page
var rootFrame = new Frame();
rootFrame.Navigate(typeof(BlankPage));
// Place the frame in the current Window and ensure that it is active
Window.Current.Content = rootFrame;
Window.Current.Activate();
So if you are using a windows phone 8 project template, with that object you can easily tell the application to load a xaml view or the game one.
You can also check how to do it with WinRT and monogame on this site (the Window.Current
is part of the WP and WinRT framework). Here, you will find how to integrate both frameworks in order to create a monogame using the WinRT xaml views :)
For more information on the Window.Current, check this link.
EDIT
If you used a monogame for windows phone template, a XAML page should already exist in your project which is used to load the game itself, as well as a media element for video and sound playback.
The page is called "GamePage.xaml", which you could use for your navigational purposes.
This info was taken from the "Windows 8 and Windows Phone 8 Game Development" book written by Adam Dawes (chapter 13).
In the case of the Windows Phone projects, GamePage is implemented as
a normal page. [...]
Within the Windows Phone page is a full-page
Grid control, inside which is another full-screen control of type
DrawingSurface. This is a type of control that DirectX can use to
render graphics to a Windows Phone page. Our XAML content can also be
placed into the Grid. A MediaElement control is present within the
Grid, too. MonoGame uses this for some of its audio playback
functionality.
On both platforms, the way that XAML and DirectX have been designed to
interact is that the DirectX rendering is processed first. Once this
has been completed, the XAML renderer then takes control and adds its
content as a second step, prior to presenting the final rendered page
to the user. As a result, XAML content will always appear in front of
any graphics rendered by MonoGame. This ensures that any XAML controls
we use as our user interface (for control buttons, text displays, and
so on) will appear unobstructed in front of the game graphics.
The XAML rendering still takes any transparency within the controls
into account, so it is quite possible to have controls that are
partially transparent or that use alpha shading. These will blend in
front of the MonoGame graphics, as you would expect them to.
With this into account, you should be able to throw an event from your game class (monogame), the xaml page can suscribe itself to it and then, when captured, render your xaml page (maybe a user control would be wiser as you won't navigate away from the main game page).
Hopefully, this will help you with your problem.