I know I need a head gasket replace but why wont it stat

Need more info , did you drain it and add filled it up, change your T stat, or was it low and your light came on ?
if you changed it, there are air pockets that get in the system, so you need to let it run with heat on and radiator cap off to get them out.
Now if it was low and your light came on, it could of just been low, or head gasket, cracked block, with a cracked block you would see coolant on the ground.one easy way to check for a head gasket, check your oil, see if its over filled, see if oil is thinner, if oil on dip stick has bubbles, must of these is signs of a blown head gasket.

sounds like a head gasket issue, was the oil discoloured white in colour, bear in mind heat is caused by friction overheating will cause damage and possibly engine seizure.. which very expensive. unfortunatly a head gaket replacment is usually not cheap either as damage tothe metal also usually occurs when the gaket leaks.

You probably have a blowin head gasket, Those car are Knowin for that (Problem)

Would have to be head gasket has fail letting oil into water jacket.. My suggestion. Does not have to be water in oil to be blown....Sorry i wpild sat head gasket......Let me ask you when the gaskets was changed did you have the head checked and did you have head bolts replaced?? Head if not cracked my need plained.......hope this helps and good luck...Please rate my posting

never-- I repeat never --use a used car dealer to do repairs on your car
The people employed are seldom qualified mechanics and they only know how to "bodgie" jobs just to get the car ready for a sale
oil will not leak from a head if the engine is running well , but oil will leak from faulty rocker cover gaskets
from your description, I suspect that when the car went in for the head gaskets a clapped out motor was fitted instead ( check engine numbers on the papers )
If you need a motor , there are plenty of good engines from japanese
engine importers
But at best do not have anything to do with that shop as the engine rebuild could be changing the engine back for your original motor

it wont go away because their is a mechanical problem and or problem with oil change [ not enough oil wrong filter etc ] will need to have vehicle scanned for the fault code to determine the problem most auto stores offer this service for free

Your car has smoke when oil is full could be valve seals,,,or head gasket, is there milky stuff on dip stick along with oil? if so its a head gasket.,,,,,,,,,,,,Also I know your check engine lite has to be on,Right?
Go to auto zone and get your codes scanned for free and ask for a printout as to what the problems are.
start there

is the weather cold if so not long

The oil change probably had nothing to do w/ it. The new t-stat may have been sticking, and causing it to over heat, and pop the head gasket.

Sounds like you have a leaking head gasket.