So, looks like the panther you want is in the hak called baba_stuff02. To have it override the Bioware model without having to add haks to the OC modules, you can extract it from the hak as FP said. Here's how:
- Open the program 'nwhak' - it's in the utils folder in your NWN directory.
- From the file menu, choose 'Open', and select the baba_stuff02.hak file - it'll be in the hak folder in your NWN directory.
- nwhak will display all the files within the hak you've just opened. The ones you want are 'c_cat_panth' (an mdl file - the model for the panther) and 'c_panther' (a tga file - the texture for the panther).
- Right click on each of those files, choose 'Export' and export the files to your override file (again, in the NWN directory)
Once that's done, the new panther model should now override the one in game. It'd be a little more complicated if the creature you wanted was not set by the hak to override a standard one, but in this case it's already set to override the standard Bioware panther.
Also, it'll override the panther in every module you play (not just the OC) while those files are in your override folder. If you ever decide you want the Bioware panther back, just delete the files from the override folder.
Hope that helps!