They have a special tool that checks continuity across all the wires to make sure they did not miswire anything. There are like 8 wires (I think) that have to be manually pressed into a cat5 jack, and it is very easy for even a professional installer to get one wrong.
Yes, it should be really loud. even a 250watt sub will sound louder than a normal car going down the road. Make sure you size the box correctly to get the most out of your bass.
No, that would take too much of my time. Your talking about the Steven King book? That was an enjoyable book to read, and I suggest you read it. Basically the boy blames the car for the death of his father, but I never saw the connection. I mean really, his dad gets ran over by a drunk...