OBDII Scanner Codes P0303, P0300: how f***ed am I?

Ok, here is another explanation.
That is oil, and your spark plugs are not sealing properly.

Remove and replace plugs, boots or wires, and valve cover gaskets.

 

Polish your valve cover as much as you want!!

I use the crank bolt to move the engine your right there and look easy rather then walk back and forth .

With a camera you should be able to look at the pistons and valve seats not sure how good you can see depends on the camera set up.

Why did you replace the radiator?

good luck!

 

Seriously I think some people come on here and get joy out of freaking people out about some terrible scenario.

If you need to identify the substance, mix it with water, if it floats it is oil/petrochemical based.
If it dissolves in water it is alcohol/water/glycol based.
Just swap the gaskets, plugs, and boots or wires.
Use Denso or NGK plugs and QUALITY gaskets and boots or wires.

 

Now after you get done with that, and if it still misses, we will help you come up with a plan. Do the simple stuff first.