If the plug wire popped out, then you probably got a misfire code. If you want to check what code it was, look here:
http://www.c-speedracing.com/faq/06.php
If it is indeed the misfire code, then putting the plug wire back in probably solved it, and you can reset the ECM by either pulling the radio/backup fuse under the hood, disconnecting the battery, or disconnecting the ECM at its plugs for 10 seconds.