Is the broken eye still on there or has it snapped off completely? If still there then it all depends on how good a quality build it was in the first place.
Any rod builder worthy of the name will put the tip eye on with hot melt glue. Try very gently heating the barrel of the eye with a cigarette lighter, after a few seconds it should slip off easily with a gentle twist. If it doesn't then it has been araldited on (a stupid way to build rods - I'm looking at you here Century) and makes it a much more awkward job to replace.
If it has been done properly with hot melt then it should be very quick and easy to replace and cost no more than about £5.