My CEL came on a couple of weeks ago. P050D: cold start rough idle. I cleared it, and took it to the dealer when it came back. They charged me $190 to tell me that it is the #7 fuel injector and is no longer covered by warranty. They quoted me about $800 to replace it. Another mechanic quoted me $360. How hard would this be to replace myself? Or is this something that is best sent to a mechanic?