Goodman Model HCA100ND4R with S8600h... heater fan keeps running after thermostat temp has been reached. If I don't shut the system down, the blower will keep running and fire never lights back up due to safety.
Is one of the sensors bad ?

Sounds like the unit is going out on high limit (overtemp). Check air filter/s first.

Filter was not too bad, changed anyway... Air flow seems to be OK... I checked the continuity on the sensor next to the fan and it was OK. The two that are close to the burner are very hard to get to. Do you think that I'm on the right track in checking those two?

Yes, you are on the exactly right track. Test every limit.