C# ASPX - REST Web Page

I am in need of transitioning an existing web application web page from an outdated post back model, to a new fresher look/feel, more interactive and fully REST web service based. See attached file for details ALL WORK CLIENTSIDE WILL BE HTML5, CSS3, JQUERY and JQUERY UI. ALL SERVER SIDE CODE WILL BE COMPLETED IN MICROSOFT VISUAL STUDIO 2010 and C#. WHENEVER PERSISTENCE IS REQUIRED, PLEASE PERSIST IN VIA AN OBJECT THAT WILL SAVE ALL OPTIONS IN A SIMPLE XML FILE AT THE ROOT OF THE WEB SERVER. I WILL WIND UP CHANGING WHERE THE DATA IS PERSISTED LATER.