Steveplatt, if you hold in the odometer reset button while starting the car it will go into "test mode" and this will display current DTCs, among other things. That's the gist of it, but you can search for more info here, google, youtube. I think you should make sure your wires and plugs are up to snuff also, you could have high resistance in a wire that klled the previous coil, the new one might handle it for awhile but will kill the new one too if this is the case.
ErikJames, you should look around here for info on the Idle Air Control valve (or IAC), it's a solenoid responsible for maintaining off throttle engine idle, and they are known to stick and cause problems like you're describing. They can be cleaned or replaced, if you want to replace it I've used a Hitachi one in the past that was about $60 and works fine, much cheaper than OEM. Search for "IAC cleaning how to" or something to that effect, it's an informative thread.