My engine normally idles at 800, but then it started to idle at 400 and was shaking. After many hours of searching through the fourms, I couldn't find any definite answers. I brought it into a shop and they told me that one of my spark plug wires was arcing down where it is connected to the spark plug. I then searched the fourms again and found a post describing the exact problems I'm having and they said it was the spark plug wires. I got my wires replaced at the dealership 3 years ago, and from what I can gather, the wires are supposed to last a really long time. So can anyone please tell me why mine could have gone bad so quickly?

Dude.. it's 3 years - I wouldn't stress. Maybe you got a slightly sub par set. And maybe the dealership didn't replace them.

They replaced them. You could definitly tell the difference b/t the old dirty ones and the new clean ones. Plus I hope they wouldn't charge me $73.68 for the plug wires and $264.79 for other gaskets and labor, when they didn't do it.