Clean your MAF sensor with CRC MAF Cleaner. Check the TPS sensor for proper resistance. Check the HO2 sensors for switching from lean to rich when at operating temperature. You can use a data logging device and program or a multimeter for those two tests.
Replace the spark plugs with the proper Motorcraft or Autolite plugs. Avoid Bosch plugs and O2 sensors - they don't play nice with these cars.
You might want to try a Seafoam treatment, too. If the TC was driven by an old couple to go get the groceries, you may have a ton of carbon in the cylinders. Do half the bottle through the PCV valve and the other half in the gas tank. Never put it in the oil as it thins it out and I never trust that.
Here's a Seafoam howto video on a Crown Vic which is same platform and engine as your TC, so it should be a good help.
http://www.youtube.com/watch?v=yibMhMADJV8