Did it just a few days ago. I have Bilsteins on OEM springs. The pro is that you can keep the springs compressed when they are moved to the new shocks. Bilsteins gives you appx. 0.9" drop. A lot more work to change springs on OEM shocks, and as mentioned earlier also will ruin your shocks eventually.
I'll try to explain in my somewhat limited technical English:
The NSX manual is a great help, and so is the FAQ. It is important to compress the springs so much that you can move them freely around the shock before disconnecting the shocks.
Start in the front with the bottom bolt, but be careful with the ABS cabel. Once the bolt and brakeline is disconnected, undo the three bolts on the top and you can use a long rod between a secure point on the car and over caliper to pry the lower arm downwards. We used a big screwdriver and pryed the shock upwards using first the hole from the bottom bolt and then on the top of the lower bolt mounting. Once you are over the top, you can drop the bottom of the shock down on the door side of the mounting and take the whole set-up out with the top first from the arch. Keep the spring clamps on.
If using Bilsteins on the lower perch, they will be the same 0.9" shorter and are quite easy to replace.
In the rear there is some more room to work the shock when removing it from the car.
The easiest way to get the spring clamps on, is using a pair and put them on the spring as far from each other as possible + as wide opening as possible. Place a jack just behind the brake disk and jack upwards as high as possible, tightening the spring compressors by hand simultainiously. This will save you a lot of work compressing the springs and is really a time-saver in the process.
We spent 4.5 hrs on the first shock and only 45 min on the last. Put the jack back before removing the clamps and slowly lower the arm while loosing up the clamps.
Finally, disconnecting the lower sway bars (?) is a good tip. Be careful int he back, and disconnect between the bar and the link before you attempt to remove the bottom bolt/link.
Or leave the whole job to the nearest work-shop, but make sure you have a firm price before they start working on the car. :biggrin: