So there is a trick to this.
A) Create a Diffused layer, place a copy of your bump map in it, set the transparency to TexAColor (make it white)
B) Create another Diffused layer, make this all of your gold settings w/ bump, spec etc.
C) Sketchup will see the first diffused layer (will show up as your bump map). So you can scale it as needed, but when you render it will show up as gold.
Rob