I want to update my thermostat. I currently have a White-Rodgers heat pump thermostat - mercury switch. I have pulled the cover off and am able to slide up the right side but not able to pull it off the wall without seeming to "rip" it off the wall. I don't want to break it as I am not to familiar with repairing or replacing. My question is: is there another layer that can be removed before unscrewing the unit from the wall or does the thermostat simply attach to the wall?

When the cover is removed you should see several screws. Loosen these to separate the thermostat from the switching sub-base. Make sure you have the power supply shut off when replacing the thermostat so as to keep the smoke inside the electrical components where it belongs.;)

Thanks. I saw the screws with the wires attached. I wasn't sure when these should be removed. I will give it a try. Thanks again for the advice.