Ronald,
For replacing the antenna cable, simply attach a drawstring or mouse to one end of the antenna cable already there and pull that through. then use that mouse line to pull the new cable into the same conduit.
If it is is standard mast lighting there will only be a wire for deck light, steaming nav light, and mast head anchor light in the standard wiring loom. An additional wire will be needed for the masthead tri-colour.
Cheers