It's certainly possible to import meshes from the game into Blender. The game's meshes are stored in the .nif format. To work with this file format in Blender, you will need the http://niftools.sourceforge.net/wiki/Blender. The plugin will allow you to import an existing .nif or export a new/modified .nif.
In regards to the second part, I'm not exactly sure what you mean. However, an easy way to assign different textures to an existing .nif is to use another program called Nifskope(which edits .nifs).