Alright, so after spending 5+ hours working on this and researching, I would like to add some notes to what has already been documented in this thread.
First and foremost, the Motorcraft YH1895 is
NOT the correct part for Fiesta STs with automatic climate control, as stated above. This module comes with only two prongs instead of five for the plug, and will only allow air to blow out of your defrost vents. The part otherwise looks identical.
HERE is what the plug looks like on the YH1895. The module in our car has 5 prongs like I said, not the two (you can really only see one) pictured here.
Next up, there's some techniques to servicing this part that made it easier. I'll describe my method below, which is similar to the one documented earlier in the thread.
1. Disconnect the battery and make sure there's no residual power left in the car. The car will have to relearn the new position of the actuator when you put the new one in. You will also be working with an airbag, so disconnecting the battery is just as important for your own safety.
2. You can remove the seat, I have the Recaro package so I opted not to. I slid it all the way back and moved the steering wheel all the way up.
3. Remove the brake pedal sensor. From underneath, twist it clockwise.
Here is what it looks like from underneath.
4. Remove the two 10mm nuts holding the knee airbag on. The right one is easy, the left one is hard. I used my smallest ratchet with a wobble extension for the left one.
5. Pull out the knee airbag by popping out the tabs holding it in place. Be meticulous because again, this is an airbag. It will eventually come free and hang from two small wires. Put something under it to prevent stress on the wires.
6. To get better visibility and allow for better light, remove
this vent by pulling it gently away from the center of the car.
7. You can now see the actuator, as seen in the middle of the picture
here. Removing it requires unscrewing two T20 torx bits, one below and one above. Removing the top one is in my opinion the hardest part of the replacement, I found it best to do it "blind" by using my right arm and left hand to guide the bit onto the screw, like
this. This prevents you from having to lay underneath and gives you a better angle to get torque on the screw.
8.
Here is the view with the actuator removed. You can rotate the big gears with your fingers in order to get the correct orientation in the hole for the new part.
9. Reverse the process. If you're clumsy and drop a screw like I did, you can remove the
side panel as shown here.
10. DO NOT start the car after installing. Reconnect the battery and put the car in aux mode (turn on without foot on the clutch) and let the system "wake up" for 30 seconds, then you can start it.
Tools I found useful: 1/4 in and 3/8 in gearless ratchets, 10mm regular and deep sockets, magnetic LED lights, and wobble extensions. If I had a right angle screwdriver, this process would be much quicker.
Does anybody know the right part to order since YH1895 is wrong?