The guy at the hardware store could have told you what to do, but maybe he felt that you should not do it. Replacing an electrical plug on a lamp or any appliance must be done correctly so as not to create a shock hazard. the wide prong on the plug must be connected to the conductor that on the lamp end is connected to the shell (threaded part of the socket that the bulb screws into). The correct plug for the application is important too. I have never liked those plugs that the wire is pierced by, although they are the most compact and best looking ones. If done wrong, something as simple as replacing a plug can get you electrocuted or create a fire hazard. I have seen people's plug replacement jobs and was really surprised how things can go wrong. then again, Murphy said it best.