Paul,
Coming from your way, the shop is on the right hand side as you enter Wondai. It is the first shop in a short line of three or four, and is the corner position of the Bunya Hwy and Edward St. If you get to the roundabout, you've gone too far.
It'll be quite a drive from Hervey Bay, but I think you will be glad you went.
I will send you the phone number. Brian is the owners name. The shop, as far as I know, is open through the week, but ringing first is certainly a good idea. Brian sometimes travels overseas, to catalogue military items for auction in USA. He is a facinating fellow to speak with. Allow yourself at least 1-2hrs to browse. More if you start a decent conversation with Brian.
Ph number to follow,