Thanks for considering Aspose.
Well, you may use InsertRow, InsertRows and InsertRange methods of Aspose.Cells.Cells class for inserting your additional headers rows/cell ranges at your specified locations. For inserting data to the worksheet cells you may use Cell.PutValue() method and for formatting cells you may use Style object attributes.
Please check Aspose.Cells wiki docs: http://www.aspose.com/Wiki/Default.aspx/Aspose.Cells/
Especially the following links which might be your requirement:
and for formattings please check: "Working with Data Formatting" section on the wiki docs.
Moreover, you may check the source code of our featured demos: http://www.aspose.com/Products/Aspose.Cells/Demos/ ( the demos are automatically installed when you install the component using its msi installer, so you may open the demo projects into VS.NET and check the source)