Hi.
This seems to be a common problem with gold-filled watches. 10 or 14 karat gold is so soft that the brushing is likely to be worn from even moderate use. I have a GF P4 that I like to wear and even with careful use, after a few months of just occasionally lightly touching the case, the surface starts to get a little shiny in places. The Omega case that I had was near mint and you could tell that the original brushing was rather light and delicate (and fragile).
Personally, I would (carefully) rebrush it. A few tips:
1) Masking
Whenever I do a bit of brushing, I use (scotch) tape to cover the areas that I want to leave untouched.The Omega is a little bit challenging due to the polished front bezel.
2) Consistentcy
Make sure to make straight, even strokes.
3) Don't Overdo It
Even though gold fill is much more durable than gold plating, it's still limited. Follow the Hippocratic oath gor watches and endeavor to do no harm. Do as little as possible.
I've actually come to appreciate the look of gold watches in some cases, especially brushed gold, which reflects the sun nicely. I'm looking forward to pictures!
-abe.