2001 Ford Taurus Shaking & Enginer Light ON

I was wondering if anyone could give me any idea what is wrong with my 2001 Ford Taurus. A couple of days ago, the car overheated and started shaking. My wife turned the car off. The repair man changed the serpetine belt, change the resivore because it was cracked, changed the spark plugs and wires and changed PVC valve. The car now runs smooth except when it is idling. It is very shaky and the check engine light is still on. Can anyone please give me some type of idea with what is wrong with my car?

Depends on what the code in the computer is. You can get this read at any autozone or other parts store. Was it shaking like this before it overheated? Does it shake at idle, or all the time? It could be as simple as a loose plug wire since those were replaced, or a number of other things.