big_smile, that's a very good start! Step 1 of Learning How To Script is indeed, adjusting an existing simple script to make it do more complicated things. (And usually then "break something", which is also a required part of the process.)
You are correct in your observation this is repetitive stuff. For one or two different items that wouldn't be a problem, but in longer lists you soon get lost.
The usual way of working with find-change lists is to build an array:
var layernames = [
[ 'FHairBowlBoy *Hair', 'Hairboy1' ],
[ 'FHairCurlyafroBoy *Hair', 'Hairboy2' ],
[ 'FHairSpikyBoy *Hair', 'Hairboy3' ],
];
The general idea is to loop over all names, check if the current layer name is "layernames[0]" (the left column) and if so, rename it to "layernames[1]" (the right column). If you know how to write a loop in Javascript, then you can implement this right away.
However .. 
A more advanced way to do this doesn't even need loop to over all layernames -- instead you can immediately "get" the correct name per layer! It's magic! Almost!
The trick is to use a Javascript object instead of an array. Javascript objects are nothing special; Illustrator's 'layers' is an array of objects, and each object "layer" has a property "name", whose value you can read and set. What I do here is create a new object, where the "name" part is the original layer name and its value is the new layer name. All you need to check for per each layer is if there is a property 'object.originalLayerName', and if so, assign its value to that layer name.
This looks a bit like the array above, except that (1) you use {..} instead of [..] to create an object, and (2) you add "name:value" pairs instead of "value" only (actually, the 'name' of a value in an array is simply its number).
So this is what it looks like:
// JavaScript Document
var doc = app.activeDocument;
// name indexed object
var layernames = {
'FHairBowlBoy *Hair':'Hairboy1',
'FHairCurlyafroBoy *Hair':'Hairboy2',
'FHairSpikyBoy *Hair':'Hairboy3'
};
// loop through all layers
for (var i = 0; i < doc.layers.length; i++)
{
//Set up Variable to access layer name
var currentLayer = app.activeDocument.layers;
if (layernames[currentLayer.name])
{
currentLayer.name = layernames[currentLayer.name];
}
}
Enjoy!