159 rear seat a/c temperature control / locking chirp

[stuvw]

Hi everyone.
I have 2 questions.
(1) In the manual there is an optional temperature control on the rear seat air vents. My 08 3.5 Ti doesn't have this, just a small shelf under the vents.
My question is, should anyone know, if I found a second-hand temp control at a wreckers, would it be hard/possible to install?
I have no idea how even the front controls allow different temperatures on each side: is it something complex deep in the a/c system or some magic near the vents only?

(2) On Youtube there are videos on how to turn off the locking chirp sound (ant how to turn it on again).
My question is do all models have the chirp installed, because mine is silent, so before trying the reverse (turn on) it would be good to know if this would be futile.
Thanks,
Stuart.

[As the day goes]

On (2)  why?  Hate the sound as a by-stander.  As it there is a clear locking sound and flashing of lights

[stuvw]

You are probably right, but I would still like to hear it to decide. Not a biggie. Question 1 is of greater interest.