I purchased an after market stereo, and when I went to install it, I never bought a wiring harness. I unhooked all the wires in the wiring harness and tried to connect them to the wires for the stereo. Did I completely screw it up beyond repair?

 

Does it work?

 

no idea, because I have no way of hooking up the new radio or the original one. I cut the wires that go to the speakers and stuff

 

Either I'm confused or you butchered your radio harness without a clue as to what you were doing. Am I close? If I am, then I'm wondering why you didn't get the harness adapter. Even so, if you've left enough wire on the connector(s) you cut off there's a strong possibility someone that knows what they're doing could repair it. Even still, the head unit could be still wired to the harness with inline connectors assuming you have a wiring diagram for the car and radio.

Moral of the story: If ya don't know what you're doing, get some help or leave it to professionals.