The code means there is insufficient exhaust gas being recirculated into the intake air system for the engine. This gas cools down the combustion temps reduces I think NOx.
The EGR systems purpose is to regulator the amount of exhaust gas being rerouted into the engine. The system turns on and off via a signal from the computer. This being based on driving conditions such as idle (off), full throttle (off), part throttle (on), cold engine (off), etc.
Did the dealer actually run tests to confirm these parts are bad or are they guessing?
The typical causes of this code are the EGR valve or piping plugs up with carbon, the EGR valve is stuck closed (often due to carbon buildup) or a electrical switch controlling the system (called a VSV) has failed. Temp sensors rarely fail.
This is not that many miles for all the parts to fail (unless some design defect). Suggest you get another opinion.
If the check engine light is off, the EGR system should now be working OK. The computer checks the EGR system operation on a continuing basis. If a problem, the light will come on (assuming it is the same trouble code).
A non-working EGR system will raise the engines NOx output and may cause the engine to have detonation (a kind of banging, pinging noise) when under load. The lack of exhaust gases causing the combustion temps to raise.
The internet is full of articles on the EGR system as this is a common problem. A Google search on the model, year of car and code will turn up hits such as the one below:
Sometimes a car manufacturer screws up on a system design or defective parts are installed that fail over time. Then a Technical Service Bulletin is issued to call attention to this problem. In this case the typically causes of a trouble code may not apply. I can't find any bulletins for this year but this doesn't mean the don't exist.