Windows Universal ComboBox custom styles

Question

Windows 10 Universal app, I have some ComboBox controls in the app. They are simply and I added them in xaml, like this:

 <ComboBox Name="cbDelType" RelativePanel.RightOf="txtDelType" RelativePanel.Below="cbRouting" Margin="0,5,5,0" HorizontalAlignment="Stretch" RelativePanel.AlignRightWithPanel="True">

In the code behind, I then add items to the ComboBox from a list. This is all working fine and I get my drop down, as expected, when I select the ComboBox.

However, I have three issues/questions with the default ComboBox or drop down.

1. I understand that the ComboBox utilized the ScrollViewer to show/scroll the items in the drop down. I would like to put a header text on the top of the drop down as it appears. For example, "Select an Item from the list below". I see that there is a ScrollViewer.TopHeader property but I don't see an easy way to set that property.

2. The scroll viewer continually scrolls. Meaning, when it gets to the last item, it wraps around the the first and continues scrolling. I don't know if I like this effect, especially when there is no header on the drop down and other styling, it is confusing. Is there an easy way to disable this so the ScrollViewer stops on the last item and you then must scroll up to get back to the top?

3. Is there an easy way to change some of the default properties of the drop down? Like making it modal, or changing the background color, selected text color, etc...?

Thanks!

Mike