So, I had my car at the dealership to do some warranty repairs. They called me and said I needed sparkplugs (they were pretty corroded and cylinder four was misfiring) and they could install them for me for $220-something... I cut them off and said I'd take care of it. I ordered a set of plugs from Amazon, along with a 5" long socket, dielectric, and anti-sieze for about $53 total. Picked up my car, and as soon as I had time, I went to replace my plugs. Turns out, the misfire wasn't because of a corroded sparkplug, but because of a weak connection between the coilpack and the spring. I ended up paying $162 for a replacement coilpack, and I'm more than a little angry with the dealership because of it.