Thermostat Replacement/Millenia

Wife's 98 millenia seems to run hot. Top hose gets super hot, and bottom hose stays cool. This even after the car has been running for a while. First sense tells me the thermo is bad. Has anyone ever replaced the thermostat on a millenia. If so what are the details of where it is located and how big of a job is it. thanks for any help u can give...