The factory head unit is not in on my 2000 mustang. I dont need a stereo install kit, it just slides in. I cant find my ford factory wiring harness. Im just going to run off my internal amp. Where is it because I had a clarion indash, but not anymore and I took out all my car audio. The speaker wires are all in the trunk from my 4 channel amp. I talked to best buy installer and he said your not going to run those speaker wires from the trunk into the HU. I guess i need to find ford harness and im golden right? Dont I just plug all the spots in the rear of the HU in with the plugs or do I need to actuall twist wires and run things? Isnt it all plug and play?