2nd plug misfired

While driving 97 Altima GXE with 128600 miles, check engine light
started to flash and remained on later on. Bring the car home and
found low on coolant(2QT). Check the code with the code reader
and found P0302, means 2nd plug misfired.

Removed 2nd and 4th plugs. 4th plug, its long wire tube and
cavity were dry. However 2nd plug, its cavity were coated with
lot of coolant, found even wetness on the outside of the plug
wire tube.

My question is that is this is a simple valve cover gasket many
of you are talking about or something else. Need your suggestions.

Thanks