Customizable sprite character using multiple layers?

Full tutorial needed

I've been stuck on this for quite some time, and I've never been able to find a full start-to-finish tutorial of exactly what I need - only bits and pieces as I searched, and half of them not even doing what I want.

What I want: -Unity to load and layer the individual sprite sheets (body, eyes, hair, clothes, etc.) together so that they appear in their correct locations. -To create a character customization menu that will automatically load resources such as hair into clickable options (so that I can add more options later without having to significantly rework code). -To be able to use this same system to create randomly-generated NPCs to populate the world. -For this system to be compact enough so that mobile platforms, such as iOS and Android, to be able to access all of (or at least most of) the character customization without hindering performance.

What I DO NOT want: -To have to combine all the posibilities by hand and import them into Unity as individual spritesheets (that's WELL over a million possible combinations, and would seriously hinder or even halt performance levels) -To have to switch to 3D models. (I'm using Unity 3D because there are some 3D elements to the game, such as the map, but I already have nearly 50 spritesheets with 8-way directional movement and complex interactions, so I'll be DAMNED before I switch to 3D characters... Plus I think they look stupid in my case.)

I'll warn you, I'm very new to coding using Unity, and pretty new to C# as well. In essence, I'm a noob, so don't assume I know anything. (I have a VERY vague idea on how to create animations, and I'm at least aware of a resources.load function. I already have WASD movement and have set up the camera to track the player character - I'm still trying to figure out how to incorporate click-to-move function and make it so they don't stack.)

These are the types of sprites I'm dealing with, so I'm a little worried that Unity will have trouble placing them in the correct positions. The bottom two are unmodified originals, but the rest have been made transparent. I can get the originals back if need be. http://imgur.com/gallery/llRpy

If anyone can whip up or find an in-depth tutorial for me, I'd greatly appreciate it. Like I said, I'm a complete amateur, so I need all the help I can get.

(Also I tried posting this in the Help Room before, but it got stuck on "This post is currently awaiting moderation," even though I thought Help Room questions could skip that??? Very confused as to why it's gotten stuck.)