Quoted:
I've been wanting to buy an extra AR lower ever since all this crazyness started. Well, unfortunately all I can seem to find are stripped lowers (at higher prices of course). I really no nothing about building AR's. How hard would it be to complete a lower? I don't want to buy a stripped lower only to find out I don't know how to put it all together!
It's not hard at all.
Written and video instructions are available all over the place - AR15.com, Brownell's, You Tube, etc.
Just make sure you have the right tools. Some tools are "nice to have" such as front pivot pin detent tool, or a tap to tap the rear pivot pin detent channel for retaining screw. Other tools are necessary such as punches (preferably roll pin punches), a hammer, and a screwdriver.
Ask in your HTF if someone is hosting a build party any time soon. You bring the beer and pizza, they supply tools and know-how.
ETA - If you care about appearance, buy some Birchwood Casey Aluma-Black. Chances are you might make an oops and scratch your receiver.