Code P0300

Hello- My girlfriends daughters boyfriend has a 98 Lumina with the 3.1. Last night it stalled out on him. He got it restarted, but it runs like crap. Very bad idle, doesnt want to restart (have to push accelerator to floor to start it and keep it running). Stalls out, can hear pinging. I pulled the codes and it says P0300.
We didnt have much time today to look at it. But I know he got a tune up with new plugs and wires about 6 months ago.
Was wondering where we should start first.......

I'm going to test the coils, check for spark, recheck plugs and wires.

I'm thinking either the timing belt or possibly the crank shaft position sensor.

What do you guys suggest???? Any help will be appreciated!!!!

Thanks
Paul

No belt, That motor has a timing chain.

Did it overheat?

It did not over heat, no coolant in oil. No coolant leakes that are visible..

the head gasket or intake gasket also crossed my mind. the car 105,000 on it. We will be checking plugs, wires, coils. Is there a way to test the ignition module?