how do the twin air vents come out?

 

 

the top twin unit

 

 

I haven't taken them out, but the wood effect trim pieces pop off easily enough to expose the lower edge of the vents (Use a plastic lever to avoid scratching anything). The passenger door side vent pops out if you push it from behind so the centre vents are probably done the same way. You may have to move the vents to the closed or open position (I can't remember which) to make them small enough to fit out as there's a white plastic linkage from the vent control to the flap that closes it that sticks out in certain positions.