I have a Seamaster I recently got back from Omega service.
One thing I will say about sending it there vs anywhere else. It will come back as if it were brand new. They replace virtually everything that isn't in brand new condition, and that's included in the cost of the service. I had a new bracelet installed on mine which obviously they will charge extra for. Their site lists everything covered and not.
Since the watch was new to me and had no paperwork, sending it to them for service also served as an authentication.
They shipped it back next day air at no additional charge, and in a new red Omega box with all the parts they replaced.
It also now has a 2 yr warranty for whatever that's worth.
Since mine wasn't a chrono, it was $700 plus $750 for the bracelet.
As a comparison, I was quoted by the local jeweler AD, $800 + parts, and $1k for the bracelet.
Another watch repair place that was highly recommeded, quoted me $500 plus parts.