I don't think it's used much. It does show up on google if you type it in though.

Yes that is correct. When Turks see someone laboring they say kolay gelsin. It's like a short way of saying "May your work be easy". Literally Kolay=easy Gel=come sin=you.

Use the verbal noun form of work. çalışma
So it would be mutlu çalışmalar.