Fun with the DoModalComponent function.

The example given in PeopleBooks is misleading. Read the description carefully -

The first three parameters are straighforward, and can be drag-dropped from the menu definition in your project (shortcut hint there).

The fourth parameter is a little different:

component_item_name

The component item name of the page to be displayed on top of the modal component when it displays. The component item name is specified in the component definition.

Note "The component item name is specified in the component definition"? Open up the component and find the page you want to navigate to.

For this parameter use the page's "Item Name", not the "Page Name".

It's always a bit nasty when the example is misleading and the explanation slightly obscured, I mean who reads the doco really, really carefully? ; )