Removing ADB Discharge Vents

I'm a complete newbie and just purchased my first used RV (2016 Leprechaun 22 ft). Trying to give the air distribution box a good cleaning, so I want to remove it from the ceiling.

I found the 8 screws under the discharge vents (and another 2 under the return grille). The side vents will allow for screw removal but the front and rear will require taking off the vent covers. This is where I need help.

This is my model:

Those covers seem like they should come loose by pressing the sides toward the middle, but it feels like I'm going to break them. And I read a review from someone who mentioned that they break easily upon removal. 

For reference, I'm asking about the items highlighted in yellow in this diagram:

Also, is it safe to remove the ADB while the A/C is running? I assume this is not advised, but I'm also in Florida so turning off the A/C is not exactly desirable 😉 

I APPRECIATE ANY POSITIVE INSIGHT YOU CAN PROVIDE!