Have a 10 ga OU Armitalia di Lucchini Ponte shotgun Where can I find assembly disassembly instructions or at least a schematic?

Sorry, but in all likelihood, you won't. There have been hundreds, probably thousands, of small gunmakers in the Val Tropia (V.T.) region of Italy. Disassembly by the owner of an O/U is generally limited to removing the forearm, opening the gun and unhooking the barrels. Further than that would best be left to a gunsmith that can find his way through a shotgun without instructions.