Changing a Stock Item to a Non-Stock Item?

We have some Inventory Items that were set up along time ago as stock items and brought into the the Branch Plant. The items are really fees, allowances, freight, and other services that do not have any inventory value but regularly have to have quantities added to inventory for orders. We want to make these item Non-Stock and just use them from the Item Master on Sales Orders. Can I just change the Stocking Type to 'N' manually or physically? And I suppose that the Item Master may have to have the Line Type adjusted to use one that does