The cylinder misfire code could be as simple as moisture in the gas - if it reoccurs, more diagnosis is required. The catalyst below eff. code could be the oxy sensor after the cat converter (there is 2 on your car - 1 b4 the cat and 1 after). How many miles on the car and have the oxy sensor(s) ever been replaced?
Since there is a lot of talk about head gasket failures in this thread, I have a quick question/comment.
Does anyone pop off the valve covers, say every 60K (when changing the timing belt), and retorque their head bolts?
Just a thought that may help the head gaskets last longer.