I don't know anything about modding ps2 files. All those formats you mentioned are used by the PC version though, so maybe the currently available tools will work with PS2.. i dont know.
when i extract characters model on ps2 for example pl00.dat, it has files like i mention above. and yes some PC tools version work on ps2 version too. i just replace items in the game for krauser's bow. but replace skin character models is hard to find where i should go first and what tools to use. because no source about modding ps2 version.
i just make video about it like this..
well this is just combination cheat and replacing item in the games.