I replace a propanecarbon monoxide detector in the RV that has reached its 7year endoflife, with the same model. I describe how to remove the trim ring, which is challenging without breaking it. Do not press straight down on the tabs to release the ring. Those tabs don't flex at all. The trim ring's slots that snap on those tabs is what flexes to snap on, but is a bear to remove.

The detector I received from eBay was dated Nov 2021, so it was manufactured almost two years ago. The lifetime of these is supposed to be 7 years from date of powerup, so I should be good but time will tell.

In the video I mention it was over thirty bucks, but I actually only paid $25.75 plus tax here https://www.ebay.com/itm/275936114386...

I had found it for about $4050 in other places and in one case, a different model and white but does the same thing and was sold for $145 plus.
I've had good luck buying from eBay for RV items, such as a water pump, steps motor, etc. at reasonable prices.