I would suggest you buy your own code reader and learn to use it. In my opinion, Auto Zone people are a bunch of "twits" that just want to sell you parts. If they were real mechanics, they would not be working at Auto Zone. In my experience, quite often what presents itself as a EGR problem is quite often an issue with the controls that operate the EGR, and not the EGR valve itself. These are not simple systems to diagnose. ...J.D.
I would pull the codes first, before you change anything. In your experimenting around, you may inadvertently cause another error code. You really cannot do much diagnostics on these cars without the code reader though. Read the codes and get back to us. ...J.D.