How to make a mod that replace existing files of the game

Hello,

I would like to replace or overwrite I should say the main.material file of etk wheels to make possible to paint Rennspecht wheels because the devs have forgotten to make it possible. So you will tell me, do it on your game files and that's done, but I would like to make it as a mod so I can share it on the repo but I have no idea how to do it and if it's possible to make a mod based on game files.

 

Ok fine, then how I do this because I didn't found any files to name and repertory my new wheels