Replacing thermostat is super easy

Please, unless you completely upgraded you HVAC unit and added staged cooling or heating... Don't settle for the HVAC people's cost of replacing or purchasing a thermostat. I did originally and got a Honeywell thermostat that only did a 2.4ghz band on my wifi, which my current setup doesn't have. The thermostat also had to be switched between hear and cool manually... I have no issue with manual thermostats, but I paid a hefty price for this one and expect it to be a lot more than what it was... So for less than I was quoted originally I picked up a nest learning thermostat

I shut the power off the my HVAC system and removed the faceplate of the original system.

Next I pulled the wires out one by one AND LABELED THEM EACH (nest came with labels, but masking tape works well too)

I then put the wires in the appropriate spot on the nest, and put the face on it.

The instructions in the nest box are amazing, they even include a small screw driver, the labels and am attachment to an electric box if that's your setup.

So please at least attempt to set this up yourself, it is not rocket science and takes less than 10 minutes (unless you have a long walk to the fuse panel)