Pull the front and back caps off by hand (upwards I think). They're just plastic. Pull the plastic cover off the outer face of the centre support (I found a plastic bike tyre lever got it off without marking it, or be gentle with a wide screwdriver.
After that, just undo all the allen key bolts. Remember which ones go where - I think there are bigger ones for the ends, smaller in the middle.
If you have the sunroof, it's a good opportunity to clean out and lube the rails. The plastic trim just pulls off after getting the rails off. You need to take out the little metal clips that will be left attached to the car and clip them back onto the trim before re-attaching. There are two sizes - black and silver. One is for the larger plastic tabs, the other the smaller ones, I forget which way round.
The trim and rubber seal for the sunroof is a bit of an art to refit - you need to ensure the rubber is just in the right place so it doesn't leave a gap or bunch up at either the front or back.
