Acorn (probably) in heater blower - how to get in there? V40

[ctparent]

It seems a critter or two set up temporary camp under the hood of my 2003 V40. At the same time I developed a noise in the heater blower that sounds exactly likle an acorn rattling around in there.

Can anyone advise how I can get at the heater blower? How do the small black anodised aluminum fasteners that are all over the place on the interior work? They do not at first appear to be screws?

Many thanks for any help.

CP