Do yourself a favor before you go buy an EGR valve just because it "could be" that. Carefully check all your vacuum line connection for cracks and splits, including the ones under your airbox at the evap. cannister. Any cracks or splits should be replaced with new rubber vac line.
Also, and probably more seriously, check the metal EGR tubes for cracks and splits. That is a relatively common area for major vacuum loss and the intake of unregulated air.
Any questions you have tonight can likely be answered by doing a quick search on "vacuum" or "vacuum lines". There are any number of recent threads walking people through this procedure.
Many suggest using some carb/choke cleaner and spraying it around your engine bay while running. Specifically around the EGR tubes, the SC intake gasket area, and all the exposed vacuum line connections. Any change in idle tone will indicate a likely leak area.
It may be that your EGR valve is bad, but it is more likely that you have some vacuum leaks.
Mike: 1997 SE w/ 183K, aka White Horse
, Gutted Airbox w/K&N, drilled 180* t-stat, tint all around, clear corners w/SilverStars, "PONTIAC" light up tail, PEMs, NGK TR55s