Depends where you are if you want a recommendation to repair one. After all, not a lot of sense recommending a place in Cairns, if you're in Launceston!
It is probably making noises because the gears themselves are unhappy. It would be easier to get a S/H unit from somewhere - try any of the wreckers, either here, or in mags like Zoom / HPI. (I got a Stagea diff sent from Sydney to Melb for around $600, a GT-R one might be a bit more)