It is pretty easy to change the fronts...the calipers are pretty easy to get off and the discs are only a few bolts if that!!
the rear calipers are 2 part calipers and you will need a CALIPER REWIND TOOL to compress the rear piston so you can fit the new pads. had to buy one from halfords...was just over £20. the rear bolts require allen keys and (for some reason) mthe rear bolts where Loctite'd in and where a pain in the ar*e to remove!! took a big hammer and some strength to remove.
All in all i reckon to change the 4 discs and pads your talking atleast 2 hours but it depends how good you are with stuff like this
Dont forget to remove the cap for your brake fluid otherwise you wont be able to compress the pistons!!
If you have any problems mate, drop us a PM and i will see if i can
help!