sedona overheating

I have an 2005 kia sedona which is overheating. I checked the thermostat and it opens so thats not the problem. Should I expect a head gasket change? What else can I do? It was puffing out a lot of white smoke from the tailpipe.

Are you sure the white exhaust wasn't just moisture since it's been quite cold lately? Does the exhaust smell like coolant is being burned? Is the level in the radiator/overflow tank dropping?

If the level of coolant in the system is not dropping, I'd start by confirming that the radiator fan or fans is/are working properly.

-Rod