Well, if you're looking for the in-game 3D models, they're stored somewhere in the game code. Since the entire game is written in Java, someone with the right knowledge of coding could rip the models from the game and export them as a more useful format, and it might be possible for you to use a program to do that (I've done so before with models from a different game before). However, if you can't get access to the actual in-game models, there are a few instances under which the game will show the wireframe of a part in the garage, so if you take a few screenshots of a part from different angles and use it as a background in a 3D modelling program, you should be able to replicate the part. Non-HD texture files are easily exported as .pngs from within the game client itself, whereas HD skins probably have to be ripped somehow; good luck with that.
but they are quite basics if you already used Maya or Blender maybe you can do them.
