Config Editing

I like to edit config files, but, ever since i finally bought the steam version, every time i edit a config file, i cant save it in the folder, so i have to save it somewhere else, then i copy it to the folder of the vehicle i want to modify, but when i go to test it, the game crashes, and my backup wont work, the game will continue to crash, then i have to reinstall. How do i fix this?

 

when i go to mods folder, vehicles isn't there, do i just put it in the folder before the mods folder?