So, I've been trying to pull off a cat ears replacer, and, well.... it didn't exactly go well. xD I completely messed up the skeleton somehow and created... this monstrosity...:

I'm assuming it's an issue with the skeleton importing incorrectly, seeing as the bones are... kinda all over the place. So... could anyone who makes animation/mesh replacer mods give a sort of tutorial on how to do this, what Blender version you use as well as the import/export(theres a few different ones but I can never find the one that works properly x.x), and how to pull it off?
I assumed you would import the original mesh file into Blender, then remesh it and reweight it to the skeleton, and just re-export and replace the skeleton and mesh files in the main folder.
...apparently that's now how it works, if my demon hellspawn creation is anything to go by.