Blend Door Actuator replacement instructions needed

Unfortunately they are correct, to replace that blend actuator the HVAC case has to be removed to get to the actuator located on the back side of the housing. To do that you need to be able to recover the A/C refrigerant, drain the coolant and then you can start on the actual repair. I attached the book information on the part itself as an image, notice the blue lines saying to remove the housing and heater cores first.
To start with you will end up removing the wipers and the cowl panel from under the windshield, then the drivers side front door, then the seat and console. That is all to get room to access the various bolts and fittings to remove the case then you remove the steering column and then the instrument panel so you can remove the HVAC case.
Once the case is out you will have access to the blend control motor.
Before I attach the images I would like to be sure you can read them first. These are how Ford now has the service manuals, pictures instead of a lot of text. Or if you wish to read up on the entire repair with all the steps and pictures you can buy access to the service information for around 20 dollars for a year for one vehicle, that also covers testing and other items I may miss in the process.
For Alldata -
https://www.alldata.com/diy-us/en/diy-repair-information
For Mitchell -
https://www.eautorepair.net/app/YearsMakes.asp

Usually clicking is from one of the internal gears in the actuator failing. To know which one is somewhat simple, which function doesn't work properly or makes the noise when selected. The mode actuator would make noises or not function if you select the dash vents, floor vents or defrost. If that all work with no noise, it's not that one. Same thing if the air door is the issue, that one is active if you select recirculate or outside airflow. The blend door you referenced earlier however controls the air temperature. If you select hot or cold and it doesn't change or you hear the clicking when changing temperatures that is the faulty actuator. Using a dealer level scan tool to check for errors in the HVAC system or to watch the door movement would also show it. However those codes don't set off the check engine light.

The recirculate actuator is an easy one to get to and test, it's directly behind the glove box door. To get to it you empty the glove box, press in the release tabs and drop the door down the actuator and connector is right there. To test it is simple, disconnect the connector and see if the clicking stops. If not it's not that actuator. First image.

The mode door is a bit more difficult as it requires the knee air bag on the drivers side be removed first. With it out of the way the actuator and cams are on the side of the HVAC case above and right of the steering column. Testing is the same, select defrost first, then switch to floor and you can watch the cams and actuator move. If they move okay and no clicking, that unit is okay as well. Changing that actuator is also simple, place the control in defrost first, then unplug and remove the actuator. Install the replacement as it is marked on it's case. Reconnect and turn the system on and off to reset the actuators. Last two images.

The temperature one however is the one you originally mentioned and it's a real bear to get to as it's located on the back of the housing. For that I suggest you have access to the service information as it will tell you how to replace the actuator as well as how to refill the coolant and A/C charge amounts. The images I used are from Alldata but are directly from Fords service information.

Okay, if it's the mode actuator it isn't that bad. Just drop the airbag in the drivers footwell and you will see the actuator up on the case over the cams and gears that move the doors as the actuator moves. The mode actuator is Ford part BE8Z19E616B, Motorcraft YH1896,
Standard Parts number ADR240 or Four Seasons 73099 depending on who you are shopping with. Rock Auto shows all of those run under $30.00.