2001 SS audio question...

I'm trying to change the rear 6x9 speakers. My little blond brain cant seem to figure out how to get the old ones out...(never had this much trouble with my Olds...grumble...) and why is there a box that looks like an amp attached to the top of the trunk with all kinds of spliced wires coming to and from it? Whoever had this car before me looks to have cut them all and halfassed putting them back. I cant even tell what they were trying to do. Could someone tell me what those are for, or at least post a link to a wiring diagram?

Look, I know I suck at asking questions, but thanks for any input you may have in helping me change the speakers and fix the cut wires...

How about starting with how to remove the back dash so I can get to the speakers...? Please?