Hi Darryn,
As Bucket mentions - the water will be nice and cold - it's at about 1100 metres above sea level.
In terms of a local guide, you'd have to just try ask on one of the Facebook forums and hope. There is one for New England NSW Fossicking and Glen Innes Lapidary club (Glen Innes Mineral & Gem Club) also have one.
The only private property you can get on besides Billabong Blue is Aroona Glen to the east of Glen Innes - but you must be an overnight camper now, no day fossicking. Look at Aroona Glen Fossicking and Nature Retreat on Facebook (It is a beautiful location in itself if you are camping).
The rest is just working hard and getting lucky in the various public spots available around Glen Innes and Inverell.