My understanding is that the B1 can indeed replace the LRU, if the fault has been identified by BITE and the subsequent replacement can be confirmed satis by BITE. Box swaps or replacements where BITE has not identified the problem are not allowed (trouble-shooting).
Furthermore, the autopilot cannot be upgraded by the B1. It HAS to be a B2 OR a standard landing (Cat III approach in VMC) is requested to be carried out by the crew. Where, on satisfactory performance is reported by the crew, the B1 can upgrade.