is this a easy task and do the rear seats ave to be removed

 

Yes, you need to remove the rear seat if it's a saloon.
Lift the parcel shelf up a little and you shoud be able to get at the top mounts.

Loosen the strut centre nut before removing the strut. It can be a pain to do off the car!!!

If you have a little bit of mechanicl knowledge you should be able to do this. Takes about an hour per strut if your changing the springs

 

might let subaru garage do it rather then local tyre garage sounds