>>318648876
What you can do is replace the fbx file in the asset folder by deleting the old one and the .meta file that goes with it and unity will automatically replace every instance of that .fbx with the new one. HOWEVER if it tries to reference something that you have deleted or changed and isn't able to it'll break. It's best to use pumpkin avatar tools for unity which is a script that allows you to copy paste all your dynamic bones, constraints, materials, and so on while properly reparenting them in just a couple of clicks.