Wires is what I'd be checking next, yes.
However - if you can find a dark enough place, what you can also do is take a spritz bottle filled with tap water, and while the motor is idling in the dark, spritz the spark plug wires.
If you get a "blue fire" around the wires, they're certainly bad
Also, treat the coil packs the same way, in case you have a bad coil pack.
Further, if you have an Android device with Bluetooth, it may be worth while finding a good ELM327 Bluetooth OBDII module and installing Torque Free on your cell phone / tablet so you can see why it's blinking the "Check Engine" light.
With the age, though, replacing the wires may not be a bad PM type thing irrespective.
Two things - 1) Don't forget to use the proper boot grease. 2) Do them one at a time so you don't forget where each one goes.
RwP