John you are correct in that an assessment is required but that can be done by the installer. However any change in the installation then it must be covered by an supporting document. In most cases this will have to be an EO mainly due not two aircraft are ever the same as a rule. But with the Triq as an example it is possible to change it as it requires nothing other than to slide it into the rack. Some Cessna VHF radios are the same.
Cheers