My car failed emission test engine light has been on awhile on 2003 Chevrolet Blazer

Results of emission koeo..........pass
communication pass
Troublecodes po128 coolant thermostat temp below po449 evaporative vent valve/solenoid cir po455 leak lg detected

Asked by for the 2003 Chevrolet Blazer
128 is most likely a thermostat failing.

the evap codes need a shop with a scan tool, smoke machine and voltmeter to determine the failure.

Thanks will that determine po455 leak also. Is this going to be expensive?
the diag is about an hour labor with the correct tools. price?? do not know what has failed. it will not be cheap, thats about all i can say.