Auth guidance please...

I'm trying to create a new method (in an extended class to Auth) to allow a user to change their password. This 'feature' is not within the current Auth Class. At first, this seems like a simple proposition, but the deeper I looked, the more "heavy" it seemed. You see, I want to put something in place that lets me change the password, but not be dependant on any particular container type. It really needs to be container blind, letting Auth handle all that backend work. But I really don't see a way, within the current framework, to do this. Maybe I'm just blind, after all, I'm only into PHP for 2 or 3 months now. Can anyone give guidance on how to approach this? This is a very important "feature" to this current project, and future once as well. Thanks Walter