how to fix black body skin? I change render mod from nextgen to any render, but it doesnt work

You have to use GraphicsMod and then activate SSS in it's menu ingame. If that didn't fix it then you are missing the skin i am using. You can either install the missing skin or edit the character and change to another one that you have.The skins i am using are Hanmen's skins, the same person that made the nextgen shaders you mentioned