You need a tool called Glow Plug Reamer to clean the prechamber opening before installing the new plugs. I do not know why you need to clean it but there must be a reason for doing so. It is possibly a $50 tool. Also, I would disconnect the battery's negative terminal before working on the plug, just to be safe.
[This message has been edited by be459 (edited 05-17-2000).]