I don’t get the diffuse color and socket part. Can you give an image?
You would only need to remake the material so it fits the new renderer. If you have image textures, you don’t need to modify or remake them, just plug them in the new setup.
Textures aren’t quite as tightly linked to a material as UVs are to the model. Each model has its own UVs, they are an inseparable part of it.
Textures however are treated as external files that are borrowed by the material. If you create a material, load a texture in it from your computer, then remove the image file from your computer, the texture will go missing in Blender the next time you open the project, because textures are loaded from external files. A single texture can be reused as part of multiple materials thanks to this way of doing things.
What about UV mapping? Can I UV map different sides?
Does blender have an option to add different materials to the same face?
You can have multiple UVMaps (up to 8), and each texture can use one of them.
A triangle can only have one material-slot, but this can have a material composed (as I show above) of two (or more) different materials.
How do I put multiple UV maps?
object data properties panel
How do I make it so that the UV map is for the side of the face I want it to be?
This is for 2.7x:
Each texture has its own mapping. each has it’s own UVmap reference.
If the same texture needs to have two UVmaps, you need to duplicate it.
(they will still point to the same image, but they will be handled differently)
Then each material (back, front, etc) can use whatever texture you have for it.
For newer versions, you can just plug the texture coordinates that you want.