I have had several GSN and MG-1's, and they are great cameras. The over/under lamps make it easy, the G's I think has the 1.7 lens. If its not working well spend a evening watching tv and work the aperture ring, winder, shutter release. Also be light on the shutter release, at about half stroke the lamps should be working. With lens cap on under lamp should light,, remove lens cap point lens at bright light over lamp lights. Put in your favorite roll of b/w film and have fun.
Forgot to add I have found nothing at our Goodwill, when I ask they show me some old plastic p&s. Have had some luck on the bidding site, you have to watch the shipping cost.