I just finished installig Eibach Pro-Kit springs onto my 2011 GTI and have the following to add:
1. I have xenons and found no leveling sensors on either side in the front. I only had one in the rear on the drivers side.
2. I have nothing to add about the rear springs as they are very easy to change out, just follow the instructions above.
3. The hardest part about the front is removing the strut/sring assembly:
a. I found it easiest to raise both sides of the car (I used 2 jacks) and undoing (by removing the nut up top) the front swaybar links on BOTH sides.
b. I also removed the 3 nuts (fully, not partially) on both ball joint brackets. This will allow the control arm to fall so you have more room to push the entire assembly down with your leg. The axles will still hit the front sway bar, but one good push will pop the strut out.
c. Definately use a strut spreader bit, makes it that much easier (I didn't even have to use any WD40 either), just don't install the bit too far in as the bottom of the shock has a tab that sticks out.
d. Leave 1 of the 3 bolts at the top in when trying to remove the bottom of the stock out of the spindle. It would be good to have a helper here. Pushing the entire spindle assembly towards the front of the car will allow more leverage for the shock bottom to pop out. Once it pops out, just undo the remaining bolt at the top and remove the spring/strut assembly.
e. I used an impact gun to remove the nut on top. You don't really need a spring compressor to compress the stock spring. There really isn't that much compression that makes the nut or spring just out at you once the nut is fully off. You don't even need to compress the aftermarket spring, just reinstall as is and tighten down the nut.
f. When reinstalling the spring/strut assembly you will again need to give the spindle assembly a good push to pop the bottom of the strut back in. Tighten the spindle bolt/nut and reinstall the ball joint bracket back onto the control arm. Then tighten the 3 bolts at the top. Finally, tighten down the sway bar link nut.
I never did an MKV suspension where you have to remove the axle bolt, but I almost came close to doing it here because it was really difficult removing the spring/strut assembly from the car. Maybe the MK6 Golf is a little easier than a GTI since the front sway bar is much smaller in diameter. The sway bar on the GTI was the biggest obstable because it kept hitting the axle while I was pushing down on the spindle assembly. Nevertheless, it's done and I'm glad.