The second link details the XML format so you know exactly what format the XML data needs to be in. You can always make some example products with the properties you want and then export them to get a sample XML file.

You can search for the CSV importer in the forums but I don't know how well it works if it does at all. You may have to write a bit of code in your favourite language to convert the flat file (ie your spreadsheet or CSV file) into an XML file. My weapon of choice would be Perl. The database and XML file have lots of one to many relationships that will be represented differently in everyone's CSV files hence the general difficulty in making a CSV to xml converter.