The glue, yeah that crap is fun. My secret, propane torch. Heat the side of the housing away from the glue, IE the back sides until the metal changes color or you hear the glue pop. Doesn't take much and don't want to break the glue holding the housing together if possible. The glue just falls out or at least the heat will weaken its grip.
The work is worth it either way even if you end up having to glue the housing back together. New filters will cost you at least 100$ They are at least available for the older models.