So the past few days My car had been throwing a P0128 code(thermostat code) than this morning it threw a sensor circuit code and I added a bit of coolant to just to work and back to be safe and on my way home my car starts blowing white smoke from both sides of engine not exhaust just passenger and driver side. Now it starts and dies immediately, is this a sign of a blown head gasket and if so how long does it take to replace one?

 

Head gasket failure will cause the oil to turn milky (oil and water mix from coolant) and give you lots of problems. Did the car overheat? If overheated it may have damaged the heads or other components. How many miles and what year TL?

 

Compression test it before you start throwing parts at it.

 

Agreed with the other 2; drain your oil, if it looks like chocolate milk, start praying. Compression test to confirm. But don't jump to conclusions just yet, to me it honestly sounds like it's simply leaking coolant somewhere, if the white smoke is coming from the engine bay.

Now if it were coming out the tail-pipe then yea, I'd start worrying about the head gasket.