I'd probably start by organizing the pieced quilts first... then start organizing all fabric by color. Just piles to start as I think once that is done you can better assess how to proceed. Maybe by then you'll be able to easily see how much you have by yardage/color and then sort it that way. Piles of reds in large yardage, medium, small. etc...
I just organized all my fabric and have a limited space to do it. I do not have as much fabric as you, but knowing that it all needed to fit into a designated space helped me get focused.
I also had a "give away pile" .. fabric I just learned to let go of because I knew I'd never get thru it all if I didn't learn to let go of some pieces.