Volvo Repair: no heat from heater: 1993 Volvo 960 wagon, heater control valve, coolant level

Question
I checked the coolant level and it is fine.  All hoses appear fine.  The car does warm up a bit slow, but the temp gauge is right in the middle where it should be on the instrument panel.  I do not smell any coolant and do not see any leaks in the car or under the car.  Please tell me it is the thermostat!  If so, where exactly is it located and how hard is it to change?  Thanks.

Answer
Annie, the heater control valve is probably not opening up to allow the coolant to go into the heater core to create heat.  Follow the top hose on the radiator and it will lesd you to the theremostat, not that you need one.  If the engine temp is normal, then the t-stat is working properly.  Roger