Yeah it's a good museum. Don't go there expecting for it to be focussed on Qantas recent heritage, but go expecting to learn about it's beginnings.
The wing walk sounds like fun. I didn't partake when I was there with a couple of AFF'ers a couple of years ago. We did take the walk through the 707, but I think we were a little disappointed that it's basically been gutted inside and converted into an executive jet (I think it was last owned by one of the Sultans of Brunei or something).
I'm certainly interested in visiting Longreach again. Count me in as Interested.