The best thing is to search this forum for similar threads etc and see what other people have done or had problems with when fitting new pick-ups. These'll probably contain little gems of advice or tips that'll help.
A couple of things that will help though.
1) Do a wiring diagram of your existing pick up and set up with regards to volume pots and tone pots. This will help you understand where wires have come from or need to go to in the rewiring stage. I would say that the new pick-ups will come with a wiring schematic and fitting instructions so that will help no end.
2) If fitting 2 pick-ups fit one first and make sure it works ok before fitting the next. This will help isolate a fault should something bugger up!
3) Put any screws, springs and other loose bits of kit into a cup or a glass so as not to loose them. Little screws bounce for miles when dropped and won't come out of hiding until weeks later when you hear it go up the hoover!
4) Allow yourself plenty of time, don't rush the job. Take care when using tools near your guitar, one slip and the paintworks chipped! Work in good light.
5) Can you solder? As the new set up will require the wires to be soldered in place. If you don't feel confident ask someone with experience.
6) The old pick-ups should just unscrew from the front of your guitar and the new ones slot into the cavity they vacated. So unless you are fitting a humbucker where a single coil used to be you won't have to chip any wood away.
7) When finished and everything is working ok, re-string your guitar and shred with a smug grin knowing you put new puppies in your axe!
On the whole it's not a too difficult task, I've done it a few times with no problems but it's fun to do as you end up up-grading your instrument. Good luck
