Is it as easy as making head textures? I couldn't find anything on youtube specifically about editing other parts other than the head.

Buy joint colors in the torishop. If you mean otherwise, try gradients and body textures.

As Skrangsta said. You can buy joints, gradients, and other items in the torishop that have a certian color. Or you can go on Market Item forum and buy for cheaper.

When it comes to textures your going to have to learn from the template given to show you how it will look on your Tori.
Head making gets easy when you know how it might turn out once you put it on. Once you figure that out the rest will be easy.
Head Template:

You can buy gradients here and here.

You can buy forces here and relaxes here

You can also buy other things such as blood, motion trails, textures, etc here