Joao,
changing the boots isn't a hard job, but it can get a bit time-consuming as you'll find other things which would benefit from a good clean/paint whilst you're in the area.
Have a look at
this post for a few clues.
The important things to know are that you will need a suitable socket for the hub nut - a normal one isn't likely to be deep enough to get over the threaded bit and sit on the nut. (I can lend you one if you need it).
Basically, its jack up the car, remove wheel, undo the hub nut (you may want to replace the wheel with the centre cap removed and drop it back on the ground to do this, but as you have an impact wrench you should be able to do it with the wheel off).
Undo enough of the ball joints to allow the hub to swing away and off the drive shaft - you can remove the bolts from the top ball joint and swing it down, or the other way and up - the choice is yours.
As it's the outer CV boot it's the easier one to get at and the new one will slide on, but you'll have to stretch it over the big bit! (but see below for an easy alternative to stretching it
)
Make sure all the old grease is cleaned out of the joint and fill it with new grease (Proper CV grease, NOT general-purpose stuff - it comes with the boots from the guys I used.)
The metal clips which hold the boot on can be a bit awkward without the proper tool to tighten them, but I use an old pair of pincers which have been ground down with an angle grinder and it's easy. Alternatively, you can use locking wire. (but if you're borrowing my socket, you can borrow the pincers as well).
Reassembly is a straighforward reverse of removal.
If all the bolts come undone it shouldn't be a long job (with the right tools) and I would expect it to take about an hour or so.
It is worth looking at the inner joint at the same time as it's a good time to replace that one if it's worn/cracked (and it makes changing the outer one really easy!) - slightly more awkward to get at, but still not at all difficult whilst the drive shaft is undone from the hub anyway - it just pulls out once you've undone the big metal band on the inner boot, leaving the inner bit of the shaft still in the gearbox, so it doesn't get disturbed and you don't loose any gear oil. If you decide to do both, then undo the inner one first, lift the outer shaft away from the car and you can do the one which is shown in your picture easily by removing a single circlip from the inner end of the outer shaft, slipping the spider arm off the splined bit, and now the outer (damaged) boot will simply slide off the shaft, and the new one slides back on. Remeber to also slide the inner boot onto the shaft before putting the spider back on with the circlip, but don't fit the retaining rings until it's all back in the car.
. That said, the manual says to use silicon grease, silicon grease is supplied with the replacement slider seal kits and it I was advised to use silicon grease by other LECers when I overhauled the stuck sliders on my rear calipers. 
). What ever the reason, my personal preferance is to stick with what was originally used.
Thanks dave, 
(i'll dig one out of my pile of stuff never thrown away and bring it up to the next West Mids meeting)
As ever a very detailed post from Dave 