Ok i get what u wanna do.
First you need to copy the boba fett .skin file and name it to another name. The file is in the same directory as the model and texture files.
Open the new .skin file and change the cape texture to the texture you want (this is your new texture file).
Create a texture with this name save as tga (I would). You could proberably do with ModView as this allows you to view the glm models without starting the game.
Sometimes in life you're the pigeon. Other times you're the statue.