Here is the link to the Shimano parts list and exploded diagram for the SG-8R25.

http://bike.shimano.com/media/techdo...9830647960.pdf

Also here is a link to the Nexus 8 service manual from the Harris Cyclery site which may be of assistance to you. It does seem to be for earlier version hubs however.

http://sheldonbrown.com/nexus8/index.htm

If working with a steel frame I would cold set the dropouts personally.