Renaming the server breaks SQL. This should float you along your merry way :)
Rename a Computer that Hosts a Stand-Alone Instance of SQL Server
technet.microsoft.com/.../ms143799.aspx
and, a bit outdated, but perhaps useful
You cannot access portal sites or Web sites, certain areas of SharePoint Portal Central Administration display the incorrect server name, and e-mail notifications contain incorrect URLs after you rename the server
