thermostat

whats up folks?  Just picked up another 99 Deville with 84k miles today and it's temp rose all the way to 255F.  No milky oil on stick no smoking nothing to show signs of head gasket (I hope).  I saw the coolant coming out of the overflow hose on the tank but nowhere else, could it be a thermostat?   Just wondering if someone could tell me where the thermo is located and how hard to replace.  thanks

Thermostat is located in cover for water pump.Its pretty easy just remove air cleaner assembly.I suggest to plastic bag over abs module to keep antifreeze away from connector.Hope it helps

thanks just wasnt sure if it was behind the upper hose or lower one.