1999 Grand AM not wanting to run

I hit a deer about a month ago and the next day my car wasn't running as well. I was told that the Catalytic converter need to be fixed. Well I had that done and it still doesn't want to run right. Now when I put it in gear is wants to die. I can keep it going but it doesn't want to. I have been told to replace spark plugs and wire so that is being done today. Then i have also been told that it could be my computer, fuel filter, timing. Any help would be really nice

Try the tune-up parts first, and post back if it doesn't help.

When you say you can keep it going, do you mean by giving it gas? Does it only want to die when it's trying to idle in gear? If so, another possibility is the mass airflow sensor.