Lots of variables. Pocket watch or Wrist watch?
IT would be good to get an overhaul (you'll probably get one anyway).
By "Coil" do you mean the mainspring (the spring you wind up to make it go) or the escapement (the part that "ticks")?
Generally, for mechanical work on spring-powered watches, figure US$75.00 - $250.00, depending on what kind of watch, what needs fixing, overhaul & lube, shipping, etc
Good Luck
Scott