Congratulations Jason, sounds as if you've got a bargain.

Dismantling the pulley clutch on the Diplomat involves a non-obvious process. Due to the ingenuity and persistence of Outdoorking members we now have a fairly detailed explanation of it in the archives:

https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=22699&page=1

To rebuild the pulley and clutch you just need to remove it as an assembly, then work on it on the bench. You do not need to get into the complication of removing the roller, so only the first part of the explanation is relevant to your needs.