As has been said it is Turnip Pilot’s toy to do with as he wishes. If he wants a quick fix and get it airborne then replacing the old radios will work, but it will be more expensive in the medium term. Regarding avionic engineers and light aircraft engineers in general – the industry does not have a good reputation but that does not mean all are bad. Like most things in aviation, it is what you know that will dictate what you pay. The ill-informed and his money are easily parted.
Rod1