Tilt Steering Column. How do you get this thing apart?!?

[Truckstr]

I've taken the tilt steering column out of my '72 Chevy pickup. I want to replace the turn signal switch and general clean the rest of it up.

The question, though, is how do I get the switch out?

I have the steering wheel off and am down to the plate that sits just above the turn signal switch. I can see that there is a very thin nut that appears to need to come off in order to cotinue disassembly.

Help!!! What size is this nut and what kind of socket does it take to get it off? Or does it even need to come off?

Thanks in advance for any (and all) help... as long as it doesn't involve using a bigger hammer.