Toyota Repair: Temperature variations, temperature variations, rapid changes

Question
I have a 97 Corolla with 100,000.  The temp used to remain constant, now it bounces around between lower temps and normal temp, never overheating.  Should I replace the thermostat?  
Thanks!

Answer
Yes, the thermostat is a good place to start if the changes on the gauge are gradual and not rapid, rapid changes indicate a malfunction in the temp sending unit or the gauge itself, in that case check the wire connection at the sending unit or try replacing it.