sounds like it is release bearing if the noise is not present whilst driving - once a release bearing is removed they should be replaced hence why its now making a noise. Lots of members on here had this issue when re-using the release bearing
there are 3 I know of local to where I live. 1of them is a GTAE lightweight model apparently they only made 300 GTAE models and 2000 GTR models. the GTX is more common but still only a few good ones left.
you really want to risk running in fresh rings with normal oil? good luck to you sir. I would never recommend that, there is a reason why you should always use running in/mineral oil for these circumstances.
Grease spots on the inner rim will be caused by a split c.v boot. If its been like this a while than your c.v joint will be knackered due to lack of grease. The noise is a sign of a worn out cv joint