Zenj, discount aviator has some good points. My aircraft type is the A320 which lends itself to the GPS apprach technique. I wouldn't like to do it in anything other, and that includes the glass Boeing type I used to fly. I would say a proper FMS system such as the Airbus FMGS with an associated instrument system iis essential. For those who don't know the Airbus, you can press the approach button on the flight control panel as if you were flying an ILS, and this puts the aircraft into FINAL APP mode which allows you to fly a non precision approach with guidance as if it was an ILS.
You mention a normal GPS. What is a normal GPS - do you mean a Garmin 250 type of unit?