Do I need to change the thermostat?

I have a 00 Olds Alero V6, My car takes a while to heat up in the mornings, when it finally warms just sitting idle on warmer days the hands goes beyond the normal, and driving it starts to go towards the Hot indicator. I only had this car about a year, I've had the water pump replaced, but I don't think my thermostat was changed out. No leaks, air is cold, heat is hot, coolant level is fine.