There are two approved ELT providers for the B-777, Honeywell and ACR, both of which have cockpit control panels and interface with the master caution system. The ELT transmitter, with internal battery, is mounted inside the fuselage skin, above the aft cabin doors and is connected to an external antenna mounted very close above the ELT.
Second item, an earlier (deleted) post mentioned MAS avionics shop. To my knowledge their shop in KL does not have the knowledge, skills or approvals to do any work on the Honeywell AIMS cabinet modules nor the ADIRU.
Third item, The CVR/FDR are mounted in hard trays, attached to major airframe structure in the tail of the aircraft. Not accessible in flight, and not likely to be dislodged from the structure during a crash. Also please remember that there is a QAR module in the avionics package that might be readable when found.