Multiple Vectors in shader/CGINC

Ok, so my problem is, I have an asset I bought and need to modify its shaders. Now, I know pretty much 0 of CG, so I'm trying to find some crazy workarounds, the main one involving somehow passing a bunch of GameObjects' positions to the shader.

Basically I want to do something like "If the pixel is within a radius R of one of the vectors from this list(the vectors being the positions of each GO), paint it black".

My question is, is there a way to pass a list, array, or something like that to the shader scripts? If so, how?

And alternatively if there is no way, (I know this is probably not the best place to ask this question, but I figured I'd use it since I'm already asking one), what's a good place to learn about unity shaders and .cginc scripts(I don't even know what language they're in tbh =/ )? Really need to do this for my project, thanks in advance!