[Chris Stewart]

An EGR valve is easy to work on. It's held in place with 2 bolts and has an electrical connector. If you can change a tire, this is a piece of cake.
They're actually a pretty reliable piece except after running up the miles and carbon gets in it.
What happens is a little piece of carbon holds the plug valve in the EGR open and the computer finds out (pintle position sensor) and sets a trouble code. Removing the EGR, removing the offending piece of carbon, reinstalling the EGR and resetting the trouble code fixes it quick. Installing a screened gasket Eric described is the permanent fix for carbon lodging. Another thing that occurs is the stem on the plug valve will accumilate a little coating which will stick it closed or open. Removing the EGR and simply working the plug valve in and out unsticks the thing and after it works freely, reinstall the EGR. I haven't heard of anyone needing a new EGR...oh yeah, don't spray anything other than air in one unless you want to need a new one.