Shock went out??, I'm not sure.. Options

[HectortheRican]

Today, I noticed a popping sound from my right front shock. I'm assuming that it just died. True or false?

[Galcobar]

Are the front struts on the sixth-gen rebuildable? If so, that would be why most DIY shops carry inserts, because it's noticeably cheaper.
That said, testing your struts isn't a matter of whether it moves when you press down, it's whether you can get the car bouncing, take your hands away, and watch it stop. The springs will want to continue bouncing, while the shock absorbers try to dampen the bouncing and bring the car back to a standstill.

Not being able to compress a strut (at all, as even stiff struts compress, or being able to do so too easily, are your indications they are blown.

That said, what you described -- the centre nut moving when you compress the suspension -- sounds more like a nut came loose. The strut rod is held into the strut mount with that central nut.