Can someone please point me to a how-to or doc on the Rich Mail extension?
If you download the extension with Integration Studio, there's a Help subdirectory that contains RichMail.chm. This is a Windows help file that describes the actions etc.

EDIT: For your convenience, I've attached it.

If you're having trouble opening the CHM file provided by Kilian, remember to unblock the file after downloading it in the file properties dialog box: