Child Window Splash Screen Close

I want to be able to do the following in MVVM:

App Startup Opens the MainWindow which in turn opens a child modal window.
The child Window will load some setting and setup database connections and populate some data from Active Directory.
This can take about 30 seconds to a minute.

I would like the child window to have placeholders for certain text loaded from the childwindow viewmodel.

Once the child window has loaded all it's values, I want to pause for 5 seconds and then close the child window and return to the MainWindow.

I can get everything to work apart from the closing of the child window once the process has finished loading and I would like to know if anyone has any suggestions.

Regards

Quentin