Face vs. Surface Types - BRep Builder

Hi,

Looking at the documentation for the type Autodesk.Revit.DB.Surface I see the following remark:

Remarks:
This geometric object is not bounded by edges or edge loops. A bounded surface obtained from a Revit element will be represented by a Face instead. 

Is it possible to extract the unbounded surface from from the bounded surface returned by a Autodesk.Revit.DB.Face?

BrepBuilderSurfaceGeometry.Create() method calls for a Surface rather than a Face - any ideas on how I can use a face from existing elements as an input to BrepBuilder?

Also - I see in the release notes for 2017 update 2 references to a BrepBuilder SDK sample, but my 2017 SDK samples don't have the BrepBuilder sample.  Both from my initial install, and then re-downloaded from http://usa.autodesk.com/adsk/servlet/index?siteID=123112&id=2484975. 

Thanks!