Not quite sure what you are asking for here. Do you want the ability to develop your surface xml and upload that without going through MySpace? If that's the case, just develop your application with your favorite editor and copy and paste when you are done. There really is no way to interactively debug client side (unless you have firebug, even then it's hit and miss) and you certainly will never be able to interactively debug server side.
Now, if you are talking about changing your HTML markup then what you want to google for is 'Javascript DOM'. There is a site called w3schools.com that can help you out greatly with that. In essence what you do is treat the entire web page (or your snapshot of it) as a hierarchal structure which you can then traverse (walk the tree). You can insert, remove, and modify any node on the tree and each node represents an html element such as <div> or <a>. Hope that helps!