Easier to do with the engine out - but can be done from the back if you remove the swing arm assembly. Plan to spend some time on this - make sure you get all your gaskets, etc. before you start. Do you have a service manual? The Honda or Clymer manuals both detail the procedure - there is not much difference between them. You'll probably need at least one special tool (flywheel puller) and that is not cheap to buy.