Contour Enthusiasts Group Archives Forums General Troubleshooting CEL and dealer diagnosis, am I being screwed?

I took my contour into the dealer for a bunch of problems today. A blown strut and heater switch resistor that were covered by my extended contract, and a CEL that wasn't.

They said that the intermittent CEL was caused by carbon buildup that was stopping the EGR from working properly, so they have to take off my intake and clean it and ****. They are charging me 400 bucks for that. I don't mind paying the 400 if the problem is going to be fixed, and these are the first probs I've really had with my car which has 52,000 miles on it. But is the carbon buildup gonna happen again in another couple years requiring getting all this work done again ? is it from bad gasoline or something?