Before anything, change that plug to another cyclinder to see if it is just the plug. If you replaced the wires due to wear, you should change the plugs too. Here is a fun way to check if it you are not getting spark. Start the car and pull the wire to the cyclinder that is giving you problems. If you are getting spark, you will feel it by a small shock going through your hand. If you have another person, you can remove the fuel pump fuse, remove that one plug, hold it and have them crank the engine a few times. You will feel it if you have spark. No shock = no spark.