All you need is a medium flat blade screwdriver (about 4-6mm) and a pair of pliers.
Using the screwdriver, insert it at the passenger end of the wiper (in Right Hand Drive countries, I don't know which end for Left Hand Drive), in the gap between the blade and the end-cap. Twist and pop the end cap off.
Now there is a soft metal pin on the top, poking into the rubber to hold it in place. Prise this pin up out of the rubber.
Slide the insert out, pop in your favourite generic wiper insert (I used Trico Multi-edge Premium), trim to length, push the pin back down with the pliers, and pop the end cap back on.
http://wiki.answers.c...ge_Astra_wiper_blades