Ok, so I need all of the html within the body tag to be wrapped within a <div class="wrap" /> that lives within the body tag (deep within it). This code needs to run from within the <body> tag itself, so am thinking we'll need to append the code to the head or add it after the first <script> tag and run it from there.
I want it to basically output the entire body contents into the div with a class of wrap on that same page (within the body), with scrollbars as needed ofcourse, so overflow: auto; and will most likely need to use .wrapInner, but am not sure how to handle it completely. So it should than be inserted into the <div class="wrap" /> and will sort of mimic the idea of an iframe, but not exactly.
As you said you need to use .wrapInner()
jQuery(function(){
$('body').wrapInner('<div class="wrap" />')
})
Demo: Fiddle
For your second question: would it be better to create the wrap element dynamically with code (from within the body), or have it be a part of the DOM from the start (from within the body)?
It will always be better if you change the markup than to modify the dom using script later