Hey LanguageWriter123,
Sorry for the not replying before, I don't think I was receiving notifications from this post anymore. It's true I haven't been active in awhile but I'll be happy to do my best to answer your questions.
Having not used NWMax in awhile this will be from memory. On the commoner model, there are the bones which are animated, and the skin which is textured. I'm not familiar with the assassin droid model, but I am assuming it is made in the same way as HK was; that is, there is not separate skin and bones, the model is animated and textured directly. When changing the animations from the former to the latter, you are essentially deleting the animations from the combined skin/bones of the droid and making it a skin only, then attaching it to the still animated bones from the commoner, not using the commoner skin at all. You should not need to "extract" or do anything to the textures on the droid, they should stay as-is through the process, since you are retaining all the textured pieces from the droid. I'm not sure exactly what issue you are running into that you would need to mess with the textures. Hope this helps, let me know if there's any other questions or if I'm not making any sense because I remembered something inaccurately. Best of luck, keep learning!
A note more in general; I wrote this tutorial long ago when I was still figuring this stuff out as I went. Looking at it now I can see some ways the process might be improved if people haven't already done it. I see no reason that one would not be able to simply delete the host skin, then for each part align on the pivot points and merge the mesh of the target model skin with the host bones, then delete the mesh from the original host bone. This would retain the original host animations, simplify the process by skipping the skinning and re-linking steps, and reduce possible complications from the bones not being the same as the skin or the weighting not transferring well. In effect it would create the same kind of single bone/skin that the droids have originally. There might be some other steps or settings to tweak I can't think of without giving it a try myself, and of course this would only work for droids or other models with no "stretchy" parts to animate, but it might be worth a try if somebody's looking to do that.