1st cylinder misfire?

Hi there, I have am 02 Ford Taurus with 167000 miles. It has been wrecked in the front end before, but no obvious engine damage occured. It just required some frame pulling and such. Anyway, I have put new spark plugs and filters in it recently, and it had still had problems misfiring a bit on startup. My mechanic said his guess was due to the fact that it had been sitting with gas in it for over a year before I started driving it. It went away, but now the engine light has come on, and it seems stall out a little at speeds of 40 or 50 mph. I can power through them though. I took it in and had diagnostics run, and he said there was a misfire in the 1st cylinder. He recommended since I had changed the plugs, and the wires were original to change the wires. I am having this done, but if it's not the case can anyone point me in the right direction based on my car's symptions (coil, fuel injector, or whatever).

Any help is appreciated!