2013 Overhead Entertainment System

Mazda CX-9 Grand Touring
Greetings all and thanks in advance for the help.

I have searched through the forums and tried to find an answer to these questions (posts are either old or not quite the same). I have a 2013 CX-9 Grand Touring (just purchased today), and it did not have the headphones or remote for the factory overhead entertainment system. I have done some searching and the replacements seem well overpriced and not available through Mazda's parts store. So, with that in mind I have a few questions.

-Are the remotes programmed the same? (i.e. can I purchase something like this on ebay and use the headphones and remote right out of the box, or would I have to replace the whole unit?)

-Has anyone replaced the entire overhead unit with a more up-to-date overhead entertainment system and can offer some advice? Would the one linked above work? Is there one that fits the existing mounts and has better features (i.e. HDMI input, better screen resolution, headphone pairing options, etc.)?

Thanks again for any help. I am quite new to in car entertainment systems.
2011 CX-9 GT AWD

I have 2011 CX9 GT and planning to convert RCA port (video in-sound L-R) to HDMI in trunk.

My project is installing additional display (10") for my daughter. She is in car seat and facing to rear. So she can not see the ceiling unit.

Ceiling unit does not have any port so far I have seen on youtube videos. Only 2 sokets.

I will share all steps If I can install it successfully.
I have been using tablets with downloaded Netflix children movies. (iPad but it could be anything else, if its only for the car the kindle fire tablet at 99$ would be more affordable and I think would work perfectly fine https://www.amazon.ca/All-New-Fire-Tablet-Display-Black/dp/B07952VWG8). There are a variety of headrest holders that you can use (you might even be able to mount it in the same location as the old entertainment system) but my kids at 3 year old was old enough to old the iPad on her laps. On the iPad there is a procedure to lock the screen so that they don't keep accidentally stopping the movie or leaving Netflix.

I know this is not exactly what you are looking for but if you are considering option 2 of replacing the unit this may be a suitable alternative for about the same price (plus you can use the tablet anywhere else when not in use in the car).