fitting springs is quite easy...but take your time. (thats very important) as its the compressing of the original spring thats the hardest and potentially the most dangerous. (dont let that put you off though
)
Once the strut is removed from the car, use the compressors (one on each side of the spring) to slowly squish the spring...keep checking the spring compresses evenly and that the compressors themselves arent trying to slip off...
once you've compressed them to a point that they are slightly loose / no force being applied to the top mount, you can undo the nut in the middle of the top mount, make sure you dont spin the the center shaft, you hold it still with a spanner while undoing the middle nut.
Once you've removed the top mount slowly undo the compressors, and pop the spring, dust cover and bump stop out...then work in reverse of that, though as the new springs are shorter its a whole lot easier to get them to a point where you can refit the top mount without issues.
just make sure you put all the dust covers,and bump stops back as they were or youre gonna have to remove the springs and start all over again...
hope that helps you get an idea of what to do...
Tools wise you only need about 4 different spanner sizes, but as you will need these if you dont have access to a bunch of them youre kinda stuck