To get the center one out you need to take the CF panel out first (2 phillips screws above the radio in the radio slot and 2 phillips screws in the top of the storage compartment/cassette holder).
2 phillips screws in the bottom of the center vents and 2 clips (push downwards gently) at the top.
To get the sidevents out you need to take off the speaker gratings first (push the clip you see when looking onto the vent whil pulling the spekare grating upwards).
Remove the 1 phillips screw that holds the vent and look for the bootomside clips similar to the ones in the centervent top.
I don't remember though whether the lightswitch panel needs to be removed first....
greetingz,