In order to get the id to update to be the username you will need to have a recordset that selects from your users table where the userID is equal to the recordset value on this details page. When you have the recordset on the page that is filtered on this user id you can use the user name binding in place of the id value that is present.
If you want to limit the records that are seen to only the user that is logged in you will need to filter on the session userID value you used in the insert. If you want the admin to see all of the records then you will either need to make a separate results page for the admin or add in another recordset to the current results page, then use an if statement to use one or the other. I think it would be easiest to make an admin all users results page that does not filter on the userID.