I have some info on the stock 2012 L450 cabin
The metal cover pops out but there is no need to remove it.
The lights are held on the ceiling with mouse-trap springs. At the spring openings, closest to the spring, there is a tab. It you push the tab back, while pulling the back cover, the cover will come off. The LED bulb is removable.
So, one could replace the stock LED bulb with a two wire Red/Warm-White LED. I plan to do this.
You can find Red/Warm-White G4 LEDs at Alibaba (China) for MUCH cheaper, but you have to buy about 100 of them. Even at that quantity, they are still cheaper than if you would buy 10+ from USA (most are made in China
anyway). You will also have some spares.
That's it. The project
list is getting longer and longer...