new disc dont. and depends on condition of rears. even so you can drop them off to be machined for $40ish
if rears are smooth and no/slight grooves then leave them and just put new pads on them. rears only do half the work that fronts do.
personally, if they in good nick but have a edge lip i would just take the lip off with a sanding wheel on the grinder. but that may not be for everyone.
vfaq here. http://www.vfaq.com/mods/BigBrakesInstall.html
you may need to remove some brake fluid from reservoir before pushing brake pistons back in.