Re: changing thermostat
Did you correctly diagnose to blame the T-Stat though? What if it didn't fix the problem after you replaced the T-Stat?
Did you make sure that the passenger side fan(radiator fan) is working like it should? It could be a bad coolant sensor, radiator cap, fan motor, fan circuit + fuse, faulty radiator, etc.
But yes, the T-Stat is easy.