1996 STS Engine dies at idle & runs rough

My wife's 1996 STS has approximately 145K miles and ran fine yesterday when I drove it to the airport. She drove it back and two miles from home it died while stopped at an intersection. She started it up, drove to the next intersection when it died again waiting for the light. She fired it up again and got it home, runs rough and service engine soon light is on. Could this be an EGR valve? If so, where is it located on a 32V Northstar and is it easy to change?

I'd check the computer codes. Since the engine light is on, it will tell you what the problem is. Read this first: http://myweb.accessus.net/~090/dtcobd2.html