CASA Instrument 12/09 was issued on 8 Jan 2009 which in not so many words give approval to:
a) specify how maintenance on an aircraft, aircraft component or aircraft material is to be carried out; and
b) are contained in any advisory documents published by CASA, EASA or the national authority of a recognised country........
NZ being one such county, the following is applicable:
The CAA in NZ have published an advisory circular AC43-14 that provides acceptable means of compliance in relation to avionics etc....
This AC covers; (amongst others)
Have a read... you may qualify?
Regarding 121.5, I believe you may find that the satellites still are capable of picking up that frequency, however many countries including Oz having introduced a requirement for the new beacon, no longer subscribe to that data. The intro date in some countries has not yet occurred so obviously the 121.5 data is still supplied .....