I don't understand why a specialized watchmaker could not repair a Pre-A.
Unless you have to change parts like the crownguard, crown, case, bezel.
For the mechanical parts of the 6497-2 movement they are pieces/parts that any watchmaker can buy, they are 6497-2 Unitas/ETA parts and they are identical Panerai or not Panerai except for the bridge but we never change an ETA CDG bridge (even I can buy them ...). Anyway you don't want to distort your watch by changing parts like hands, dial, movement bridge. So I will go through a specialized watchmaker rather than Panerai to master the parts to replace.