Navigation using RelayCommand<T> in MVVM Light

I have been following Jesse Liberty's tutorial on MVVM Light for Windows Phone 7, but I'm stuck on this problem. I need to navigate from a main page to a detail page. Following the tutorial, I'm using a RelayCommand in the MainViewModel:

public RelayCommand<Customer> DetailsPageCommand { get; private set;}

I then initialize it in the constructor:

DetailsPageCommand = new RelayCommand<Customer>((msg) => GoToDetailsPage(msg));

Finally you implement the GoToDetailsPage method:

private object GoToDetailsPage(Customer msg)
{
    System.Windows.MessageBox.Show("Go to details page with: " +
        msg.First +
        " " +
        msg.Last );
        return null;
}

Showing the message box works, but I'm not sure how to navigate to the detail page instead. In previous sections of the tutorial page navigation was handled with something like this:

var msg = new GoToPageMessage {PageName = "DetailPage"};
Messenger.Defau开发者_如何学运维lt.Send(msg);

You'll need to register to receive messages of that type and then navigate appropriately.
The following assumes a page name and that you're navigating to details of the specific customer by passing their Id in the query string.

Messenger.Default.Register<Customer>(
    this,
    c => NavigationService.Navigate("/Pages/CustomerDetails.xaml?cid=" + c.Id));

You'd then adjust your code accordingly:

private void GoToDetailsPage(Customer msg)
{
    Messenger.Default.Send(msg);
}

I hope this helps.