code P0300, engine overheating after installing new spark plugs?

The vehicle listed above is an EX (1.6-liter I4 hybrid engine). I was driving and the car stopped being able to accelerate and check engine light came on. P0300 code came up. Figured it was the spark plugs as car is almost 100,000 miles and still had original ones. Changed them (never did this before fyi) but was running fine after. Then after driving for several minutes, the engine overheating sign came on. Not sure what happened. I had some trouble with one of the hoses connected to the engine cover. Any ideas would be greatly appreciated. Thanks.