If you just want to change the font this MIGHT work (use a copy because I didn't test it)
Code:
Sub WordArty()
Dim osld As Slide
Dim oshp As Shape
For Each osld In ActivePresentation.Slides
For Each oshp In osld.Shapes
If oshp.TextFrame2.WordArtFormat >= 0 Then
oshp.TextFrame2.TextRange.Font.Name = "Arial"
End If
Next oshp
Next osld
End Sub