1968 Omega Sea-master 145 016 Chronograph

If you intend to sell it, just polish the crystal to make it look a bit better (will need changing anyway).
You should be able to get more than $1K for it easily.

If you decide to keep it, get it serviced and enjoy it.

Good advice. It's a pretty clean watch with a bracelet. If you polish the crystal (with a cotton ball and toothpaste, or order a small tube of polywatch from amazon), hopefully people can see that the dial doesn't have scratches, nicks and dirt. Assuming it's a clean dial, your estimates seem realistic. 700 for servicing and more commission, it gets harder to sell and people want a better condition case. 3k doesn't seem unreasonable if you service it, but the case will hold it back as the price rises, imho.

Describe it honestly, clean the crystal, take clear photos like you did here, and it should sell without a service. It's more work to sell it yourself but that's why dealers can get away with low offers.

Of course you could service it. There's satisfaction in seeing it in its best light and not having to worry about returns. You may get more money, or you might not get the service cost back. However, if you want the satisfaction of getting the highest sale price and are willing to wait the time to get it serviced, get it serviced and see how it does. But most people will likely suggest you not service it if you plan to sell it.

Good luck either way.