2001 Other Chevrolet Models ignition coils

My husband and I were told by a mechanic that we need ignition coils for my chevy tracker, he put in new plugs and checked it in the computer and told us that the ignition coils wernt firing right, we bought new ones and put then in and we reset the computer by taking the battery cable off. The problem is that is is skipping once in awhile and the service engine is still on, does it need to be reset by a machine or its some thing else, we just had a cam sensor put in it too.