I was wondering how would be possible to gold or silver plate this
items without damage the oxidised details,
No, plating requires absolutely clean surfaces. That means no
oxides, dirt, sulfides etc. Otherwise the plating will not adhere to
the base metal. The processes used to achieve the level of
cleanliness required for plating will remove the oxides on your work.
If the areas are recessed you could paint the lower areas dark after
plating. Otherwise you will have great difficulty in getting the
effect you desire.
James Binnion Metal Arts