Passanger airbag + scuttle seal

[D.Slatford]

I've almost got the dash out of a 1998 Xantia Estate to replace the heater matrix, but of all things, the passenger airbag has gone and held me up.

I had wasted valuable daylight hours removing some 17near-impossible-to-reach nuts to try removing the cover, but still it would not budge, then discovered another row of nuts right up where I couldn't locate any tool.

So, figured it didn't strictly need to come out and just unplug the cable, but that seems held down by two peculiar nuts I also don't have a tool for.

Are these some sort of "special" nuts for which I need to find a particular socket? It'd be great to know in advance of next weekend when I (hopefully) tackle it again!

Also, is there any special sealing strip I should be looking for (as Haynes suggests) to reseal the scuttle panel, or just a liberal squeeze of silicone sealant? The old seal had completely perished, replaced by mud!