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Generally, using grease or oil lubricant on safe parts and locks is inadvisable. It can gum the works up badly. Silicone powder type lubricant is listed for safes and their latches.
It may not work for long even if you do reassemble it... though I confess, I don't have information as to how that is done. Since that is the case, I have Opted Out, with the suggestion that the oil/grease lubricant be cleaned off the parts before they are reassembled.
(Incidentally: was there any rust on the inner working parts? or was it merely 'dusty'-looking?)