Service Engine Light

I have a 99 Alero and the service engine light comes on all the time. When it comes on the car smell of gas and blows out white smoke. I had my brother-in-law get the codes and it came back with P0306 & P0206. Any ideas on how to fix the problem?

Sounds like a blown Head Gasket!
1) White smoke
2) P0306 - Misfire
3) P0206 - Injector problem

Is the coolant resevoir tank contaminated with oil or gas?
Check Engine block oil
Check coolant level