Check Engine Light on 98 corolla

[240meowth]

Hello guys, I've been on this forum once before and you guys have been more than helpful! But I ran into another problem with my g/f's car. I degreased her engine and started the car, it all ran fine, till i drove it for some time and than it became really hesistant and the check engine light came on. I drove it home to find that piston #4's spark plug didn't cover up the spark plug hole and water got in it. I used a towel to suck as much water out as i could and unplugged the battery for the ECU to reset. It worked well for a few month, now the check engine light came back. How do you check the check engine light on a 98 corolla?

Also, I am trying to find a new set of spark plug wires for her, I was looking for OEM stuff, but it costs 70 dollars at kraygens. Anyone have any sugession on decent spark plug wires for a decent price?

As far as spark plug goes, does the 98 corolla do well with platnium? Because Bosch has a deal going on right now that if you buy 4 platnium spark plugs and an 02 sensor you get 20 dollars off your gas purchase or something. And speaking of 02 sensors, it was 160 bucks at kraygen each... Where can i get a better pricing on Bosch 02 sensor?

Thanks guys, i'm noob w/ corollas!