well, if you're making your own mod just include the hak in it in the toolset under module properties in the custom content tab. Though you have to be carefull about conflicting 2das.
To unpack a hak for use in your override directory use a tool like NWViewer or NWTool, theres quite a few out there, look on the vault for them. Once you extract the stuff from the hak put it in your override folder.
I strongly suggest keeping multiple override folders for various uses and swapping them out when needed
i.e. rename your current override "layonara - override" or "default - override" and then make a new "override" and place the new stuff in there. Then to switch back name "override", "PrC - override" and "default - override" to "override"
This is neccessary because having weird stuff, ESPECIALLY anything that modifies classes may render characters invalid on servers that enforce legal characters. This is to prevent exploits using class overrides (like deciding to override the fighter class so that any ftr you create gets every feat, dragon wings and +40 str at 1st lvl and then trying to log onto a multiplayer server with that character.)
