Can just the temperature control knob be replaced?

That car likely has heated seats, but they are not working for some reason, GM doesn't install the panel with the seat control if it isn't used. No, the two are not interchangeable. Replacement isn't difficult, you use a flat trim tool to remove the right side dash pad, then remove the control head by pulling its clips free. Replace the head and reinstall the trim panel. The knob could be replaced but you need to disassemble the controller, unsolder the bad control and install the replacement. The replacement would likely need to be sourced from a salvage yard as they are not a part that is considered replaceable at a dealership.

Thank you for the reply, Steve. The vehicle has cloth seats, so I thought that it wouldn't be heated. The vehicle has the heating/AC control panel with buttons to heat the driver and passenger seats, but when you press the button, they don't light up.

If those two control panels aren't interchangeable then I'll just replace it with the one currently installed in the vehicle. Is there any programming that needs to be done after the new heating/AC control panel is replaced?

Cloth can still be heated but it may be disabled for some reason. Service info says no programming required which makes me suspicious. I would suggest at least doing an actuator recalibration. For that find the HVAC control fuse and pull it for at least 10 seconds. Then plug it back in and start the engine. It should take about a minute to do the recalibrate sequence and that should be it. That fuse is in the panel on the left side of the dash. Should be a 7.5 amp.