Here's my write up of my install to supplement Osunick's (OP).
The one thing I learned is that Tesla keeps optimizing their builds, so be aware that the install will vary depending on your car's build date. Mine is July 2021.
I ordered all my parts directly from the service center as noted in my previous posts. No issues and no problems ordering and picking up the parts. Price did increase and probably due to the delivery delays and material shortages. Total costs to me was $115.76 for each part- the control switch and the lumbar support.
Use the tools stated in OP's first post and read through his instructions. These are just a supplement with photos.
Head rest removal. You need to gently pull or push down the vegan leather until you expose a gray/ galvanized metal wire clip that slots into the black plastic bracket/holder the headrest metal posts sit in. Use a trim tool or flat head screw driver and press the metal wire to the left and away from the plastic bracket. Pull up on the metal post and it will slide up a little. Do not let it slide back or the metal wire clip will lock it back in place. Do the exact same thing to the right hand metal post. The wire clip is set up in the exact same position on the left.
Your head rest should now look like the pic above. Just pull up a couple inches more and you are good. You do not need to remove the headrest completely but I did for my install to just get it out of the way.
The two metal posts of the head rest holds the rear plastic liner of the seat in place. Use both your hand and gently but firmly pull along the top edge evenly until you hear a pop sound. Once it release you can pull the back liner all the way down. It sort of hinges with two plastic hooks near the bottom. You can see the two slots in the metal frame at the bottom of the photo.
You can now see the existing yellow lumbar frame. At the bottom of the frame you can see the 10mm bolt and the black elastic fabric with thin plastic retainer/ clip that is holding the bottom of the yellow frame in place on the metal frame. You need to remove the bolt and unhook the fabric plastic retainer to release the bottom of the yellow frame.
Before you remove the yellow frame you need to remove the wiring harness. On the bottom left you'll see the connector which has a release tab just above where you see the wires attach. Press on the release tab and gently pull the connector up. Try not to pull using the wires because you can damage the connector.
I decided to remove the yellow frame first. You do this by unhooking the bottom of the yellow frame from the metal support at the bottom. Then push up the entire yellow frame with it's two metal posts at the top. You'll see that the metal posts sit in a metal receiver at the top. Just push the entire assembly up until the bottom clears the metal rail support and then pull the bottom away and down. Once the metal post clear the housing above, you are golden.
Next is to remove the wiring harness from the yellow frame. The original post says to twist the connectors clockwise and/ or anti clockwise. I found I could not get them to release, so I turned the yellow harness around and pressed on the narrow ends of the connectors to release them through the opening in the frame.
Press the ends indicated by the red arrows.
I can only attach 10 photos max to a post and will continue in the next post.