Need Help on Modding the races

Hello all. I was wondering if someone can show me how to use the Mod folder. I want to replace a few of the races with a custom race included with their own backstory and pictures. Same thing for the minor races as well. What files should I be looking at? Also, i would prefer to use the mod folder so I can always turn the option off and play the regular game. Anyone know what files goes in what folder in there?

Oh, and is there a way to replace say the standard battleship with a custom ship i made through the ship builder? So in that case, when I create my custom races, they would use the custom ships.