Mazda-Protege 1999 is overheating after some minutes of driving It may be the thermostat that is not working well if si how can you replace myself?

Check the timing belt Answer - My 99 Protege was leaking out coolant slowly out of the water pump. A seal on it had gone bad and the pump needed to be replaced. Haven't had a leak or an overheat since new pmp was installed.