These can be deceptive: they always look bad when they are dirty and unloved, but often clean up far better than you would imagine.
I suggest yours would come up nicely (no polishing!) with a new crystal, movement and bracelet service from an Omega licensed watch repairer, and a good clean. It will still look used, but full of character, whereas if you ask Omega to do a factory service it will come back to you looking like a new watch.
The main thing is to instruct the repair guy NOT to polish or brush the case. If you want to see why, just cruise through Chrono 24 examples of shiny, over polished cases.
I speak from experience, having carefully taken a slightly shabby Flightmaster through this process a year ago. I am very happy with the result.
If you live in Canada I would suggest contacting
@Archer through this Forum.