A few questions regarding rigging for a newbie...

I am coming into Unity from an animator's perspective, using Maya to model and rig my characters. I have done a few tutorials about basic rigging, so I have a basic grasp on the process. I have a few questions, since I don't know the correct terms for what I need to look into in order to keep learning.

What I am trying to do is have a single rig for a particular character. The character will have different accessories or outfits that the player can switch out. This is seen in many games as changing armor pieces: the character changes pants, but his torso stays the same. He adds glasses, and glasses are bound to the head while the rest of his equipment stays.

What do I need to look for in order to find the right tutorials on that?

I assume these questions will be answered in the tutorial, but I figured I might as well ask them while I am waiting here. I would assume you are just switching out visibility on different meshes that you have included in the same object, all skinned to the same skeleton. But if that is the case, wouldn't you need an obscenely big texture map in order to fit every single texture onto the mesh?

On that same thought process, if I were to decide I wanted to add in more armor pieces later on, would I have to re-rig and re-skin the entire thing, or is there a method to adding in new pieces a bit less painfully?

Onto a further question, how does facial animation work in Unity? Are blend shapes supported within the engine? I am most familiar with blend shapes, but I am open to any good tutorials that would assist me in my work.

Thank you so much for your time!