the rear brake disc is rather easy, there are 2 12mm bolts holding onto the caliper, take those out, then take the right rear tire offf, i forgot if you have to take the hub off, if you do just zap the big bolt off. Then take off the 4 allen head bolts off and your good
if you press it you wont have to bleed, just use a c clamp to compressit back. Only time you may have to bleed is of you disconnect the caliper from the line, raise the caliper over the resivior, or run it too low on fluid., at that point I bleed up from the caliper side to the resivoir ( air rises ...another topic if anyone wants to be first.... :grin_nod: )
If you never took those 4 bolts out that hold the rotor to the hub, heat them up with a torch first, they have a high grade lok-tite that holds bolts better than I've seen anything before. After there heated they should come out with a little elbow grease. you shouldn't have to take your hub off either, the rotor will fit around/over it.
Yes you need the diaphram, if it's spilling fluid then you put in to much. Sort of a self leveling system :grin_nod: There are full/add markes on the resivour.
Since the early models had a recall on the rear brake I usually fill mine a little above the full mark and put a rag around it when I put the top on, keeps the air inside to a minimum.