Likely you have no need to visit the dealer. To clear your code you need to clean your EGR diffuser and your MAP sensor. The video is below.
The EGR causes a lot of troubles on this truck. The exhaust from the EGR cokes up your EGR diffuser tube, the MAP sensor and the intake. Worse yet, when the EGR cooler fails it starts pushing coolant into the intake. A hybrid diesel/steam engine is not a good engine. The only way to stop all this nonsense is to turn off the EGR valve.
That is a lot easier to do when you don't live in California. Hopefully someone from California will give you good options. I would not trust the dealer or the last guy's oil change either. Get a new filter and 11 quarts of Rotella T6 and change your oil.