While driving down the freeway this morning, I pulled over after I began to lose power - I was pushing the gas pedal all the way to the floor and just kept losing speed. Only when I stopped and saw the steam blasting out from under the hood did I realize it was overheated - my digital cluster is dead (again) so I have no temp gauge or warning light.

After letting it cool off for a few minutes, I started it again and carefully drove to the wal-mart 2 miles ahead and picked up a jug of pre-diluted coolant. I poured that in and now it seems to run OK, however it looks like one cylinder is not working correctly. It feels very rough while idling (rougher than before, that is) and when standing next to it you can hear a "pinging" or "ticking" sound as it runs. It feels fine while driving.

So, how screwed am I? Do I just need some new spark plugs or is the whole engine shot?