EGR Systems do get plugged up with carbon, this is normal, not at all bogus. I would recommend replacing the EGR Valve since they have to remove it and have them clean the rest of the system. Is this due to a check engine light coming on?
If there aren't any issues, then they are recommending this as a preventative maintenance service, and it is up to your discretion. If the system was to plug up, the check engine light would come on, and you would have to pay a diagnostic fee to verify that was the issue and then have the system cleaned out. So by doing it now you possibly prevent that from happening. How much are they quoting for the job?