Hi,
My advice is don't get the code using the download links on codeplex, use Tortoise HG to get the code correctly.
The content is stored in the database so if you are using the same database connection string then you will still have the same content after updating the source code.
Most likely problem with the design is either the skin files did not get copied correctly from /Data/skins to /Data/Sites/[SiteID]/skins (/Data/Sites/1/skins)
or file system permissions on the skin files are bad. Use firebug or browser dev tools to see if any files are not returning ie 404 or other error code.
Hope that helps,
Joe