The star nut actually holds the spring seat in place, so you can take the top nut off. For safety, I don't unless either the car is on the ground or I have a spring compressor on there, you just never know.

Comment on the FCP video, they show the tech using a drift or wrench to tighten the star nut. That's a no go, star nut will loosen right up. Make a 4 side socket (you'll see when you see the star nut) from a cheap impact socket. If you don't have an impact gun, get a hand impact, you need to get that sucker torqued or it will loosen up (ask me how I know). Once strut is back in car and car is on ground, you can remove top nut and tighten star nut with some kind of impact. Good luck.

Impact works best here, or if its the old strut you can try a vice grip on the shaft, but I've never had any luck with that approach. The star nut comes off easy with a few taps, but it needs to be tight after reinstall with new struts. I suggest re-installing on car with out top cap and "making" a 4 slot tool from a harbor freight impact socket. Blip it a couple of time with the impact gun to make sure its tight, then spin on the top cap and nut. You should be good to go. good luck.