If you've done front pads the only real thing different about doing rear disc pads is that the caliper piston needs to be wound back it but there are plenty of videos on you tube to show you the procedure
e.g. http://www.youtube.com/watch?v=rlMU8K36Hjo&feature=related
take a look, you'll need to clamp the flexy before pushing the piston back so that you can let excess fluid out of the bleed nipple. That way you won't risk flipping the master cylinder seals. The cube tool can be obtained off ebay for about £7, see
http://www.ebay.co.uk/itm/Draper-3-8Drive-Brake-Caliper-Wind-Back-Cube-Tool-52334-/140653309479?pt=UK_Hand_Tools_Equipment&hash=item20bf972e27
Browse through youtube because there really are plenty of helpful videos that cover the whole procedure in full detail.
ChicksFan
December 2011