You can check the SWTOR Slicers wiki and Discord server for info about getting the TOR assets into Blender, baking tints into textures, etc. - https://github.com/SWTOR-Slicers/WikiPedia/wiki
After that, it's not any different to porting any other 3rd party asset into KOTOR. For things like completely new creatures, you could conceivably import them with their original TOR rig and try to use their original TOR animations. Although TOR's animation system is very different, so you'd have to do a lot of custom merging/blending to get what KOTOR needs.