Normally is not an issue but is up to you. You can shade off one or two details (eg geran number) if you are worried but I dont see any purpose as gerans are public documents and can be easily obtain from the land office with a small payment albeit some inconvenience

You may 'worried' about his intention but at the same time he may also 'worried' if you are the owner.

He may also want to confirm the exact details b4 proceeding further.

As a seller, you should be concern who comes to view the property. He may turn out to be a robber. There is a reason why many appointed agents to handle a sale or rental. Not that agents can 100% avoid such incidents but they have ways to screen and minimise it.