I was curious of how this is done also, I'd like to find out where the material path is within the directory and what sort of plugins are required to edit them within photoshop. Ofcourse if it's a complete different ballpark then a tutorial would be nice for everybody
I'l make one on how to skin if you want. To save me the job though, the basic thing to do is download paint.NET and open the corresponding .dds in the cars directory (the .dds files are named intuativly so finding which one you want is easy). The .dds is basicly a very simple image file that can be quickly loaded by the game. When you edit it just overwrite the original and you will have a skin. There are normally 4 diffrent dds files for each part that has a skin. you want to edit the one ending in _d as it will be clearest when you load it back in. avoid the one with _n as it is a normal map used for adding detail to the car via textures and isn't really meant for editing. the opne with _s is a specular map used to decide how shiny stuff should be. I hope that helped to some degree and if your still struggling i can make a tutorial but i have a feeling there's already one somewhere Rob
There's already a tutorial for making skins. http://www.beamng.com/threads/2796-Tutorial-How-to-skin-your-own-vehicle?highlight=tutorial