g =
  Graph[{2 [DirectedEdge] 3},
    VertexLabels -> "Name", EdgeLabels -> {2 [DirectedEdge] 3 -> "hallo"}]

g1 = VertexReplace[g, Thread[VertexList[g] -> ToString /@ VertexList[g]]];

g =
  Graph[{{1,2} [DirectedEdge] {2,3}},
    VertexLabels -> "Name", EdgeLabels -> {{1,2} [DirectedEdge] {2,3} -> "hallo"}]

In[15]:= Fold[
 SetProperty[{#1, #2}, VertexLabels -> ToString[#2]] &, g,
 VertexList[g]]

During evaluation of In[15]:= SetProperty::pvobj: $Failed is not an object with properties.

Out[15]= SetProperty[{$Failed, {2, 3}}, VertexLabels -> "{2, 3}"]

g =
  Graph[{2 [DirectedEdge] 3},
    VertexLabels -> "Name",
    EdgeLabels -> {2 [DirectedEdge] 3 -> Style[" hello ", Background -> White]}]

Fold[SetProperty[{#1, #2}, VertexLabels -> ToString[#2] <> "*"] &, g, VertexList[g]]