Not hard at all if you have some basic skills. The only tools i used were allen key, socket wrench and some extensions. You could probably happily do it with a allan key, i forget what size i used but im sure someone will post the size needed.
If its a k04 then the valve will be at the front of your car, if it is a k03 it will be under neath the car towards the back by the turbo on the driver side. Its three bolts. the higher you can the the car the easier and I found removing the skid plate gave me just that little extra room to work with. Theres loads of DIY and instructions online.