how to change backseat reading light bulbs on Navigator (expedition?)

I've got a 99 Navigator and one of the back seat reading bulbs is out.
How do I change it? Do I pull just the clear lens off the fixture....or do I
pull the entire fixture out of the headliner?
There is nothing about this in the glove box book....or the 360 dollar set I bot from Helm.
I'm usually pretty good at this stuff....but this looks like a good opportunity to ruin a headliner.
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