For most purposes, you should treat the JSF servlet as a black box. It exists primarily to dispatch and control the application, and, like my radio, there are "No user-serviceable parts inside".
If you truly want to understand what it does, the first thing I recommend is that you gain a good understanding of the JSF lifecycle and how it manages component trees, so that you'll know what it has to do. Then get a copy of the servlet source code and see how it actually does it.
Customer surveys are for companies who didn't pay proper attention to begin with.