According the link I posted from the Qantas website, their BASE maintenance is done in Brisbane. Base maintenance is the major stuff.
Cut and paste from Australian Aviation magazine: Somewhat less than the "many hundred" you mention
Qantas head of engineering Chris Snook said the AD was “very deliberate”.
“What we saw is what we thought we would see if a crack would occur,” Snook told reporters.
“I think there is an integrity issue with the component on the basis there is an AD related to it. There is not an integrity issue with the structure. There is redundancy built into that structure.
“The load limit on that structure hasn’t been compromised by this crack.”
The airline had no 737-800s with more than 30,000 total flight cycles.
Virgin Australia has said previously it had completed checks on 19 of its 737-800s affected by the AD and found no cracks.
Overseas, there were about 50 aircraft that have been grounded after cracks were found in the “pickle fork” component, Agence France Presse reported.
Other sources have suggested that it may just be a manufacturing fault with that particular component as they changed from a wholly machined item to a forged item at some point, and may just be related to certain batches.
In any case, there is redundancy built into the structure, and they are removing anything with cracks from service until repaired so all the panic is completely unjustified