alright, my 1991 Civic DX hatchback failed the local emissions test. If there are common and easy parts for me to swap out, I'd love to do the work myself before I hand it over to a mechanic and pay for the work. Problem is, I don't know what would need to be replaced? I was figuing a standard tune up could help as its been a while since I replaced the spark plugs and wires, but is there an O2 sensor I should look for as well?

I can summarize my request to this. I'm looking for a list of things that I can replace in my car with relative ease that could assist in helping me pass the emissions test. Any advice would be greatly appreciated.