Hey Paul, this is definitely not a fast and easy task, takes quite a bit of time and patience. It helps a lot if the vent assembly is out, make things a whole lot easier. Basically, the only tool needed to release the clips is a thin sharp pointed metal pick. You only need to release one clip and the whole vent piece should pop right out, it's held together with friction only. Insert pick between one of the vent pins and the clip and pry it outwards, pry from both side of pivot pin with a lot of gentle persuasion. Do not pry elsewhere other than the inside or parts of the plastic clip may break, rendering them useless. Use extreme care in prying out and not damaging the plastic clip as they are no longer available. Hope this helps.
These are the disassembled parts
The two exact plastic clips-top clip faces out outwards
Insert pick between vent grill piece and holding clip---pry from both side of pivot pin
The clip is almost out, keep on prying outwards
Bert
72 3.5 CSi
88 M6