How is your coolant level? If it's low, I'd check the entire system over for leaks before I did anything else (hose condition, leakage around water pump, etc). If it checks out fine, might want to swap out radiator caps as they tend to fail over time.
As for the thermostat, it's a 10minute job and one that just about anyone here with a socket-wrench could do. I'd pull the thermostat and test it out first before commiting myself to a replacement. If it turns out fine, I'd start eyeing the water pump for replacement.