Check engine light is on

just wondering if someone could tell me where to start on this. i have 4 codes and perhaps they are related to each other and could have one common problem, i dont know.

P0455 evap emission control leak
P0128 coolant temperature (ECT) below thermostat regulating temperature
P0606 PCM processor fault
P0014 camshaft position timing over advanced (bank 1)

this is on a 2004 envoy XL with about 85000 miles.
i just wondered where i should start? i was thinking of replacing the thermostat first. then maybe checking vacuum lines with some starting fluid. maybe replace the cam positioning sensor?

Yes the t'sat, but the other codes need a proper diagnostic process, I would suggest a factory manual or a subscription to alldadta.com for the trouble tree that will pin down the issues.

I have a 2005 GMC Envoy w/ inline 6. My MIL light is on throwing codeP0014. I pulled cam actuator solenoid out and cleaned the screens and reinstalled. after about 30-40 miles it came back on. Is there a way to test the solenoid to be certain that is the cause? part is like $50 and all the screens were in tact so I didn't want to replace for no reason....appreciate the help
thanks
Smitty