Replaced Fuel intake Valve Seals now New Problem

[NCJETSKIER]

I took my car (and the parts) to a dealership and had my fuel intake valve seals re-sealed on my 19197 E300 diesel on the injector pump. Did not even make it out of the parking lot after the work was done and the check engine light came on. He put the analyzer on the car and it stated EGR. We checked all the connections and all seemed fine. What could he have done to cause the Check Engine light come one and give an error code for the EGR? Could there be an air leak?

Also, how do I clear the Check engine light on the dash located on the far right side?

Thanks for any help!!!!