What I generally do with Excel is to add this 'using' alias at the top of the file:
using Excel = Microsoft.Office.Interop.Excel;
I then prefix everything with Excel. So the call to this method would become:
Excel.Application oXL = new Excel.Application();
(Type: Excel.XlFixedFormatType.xlTypePDF, Filename: "sales.pdf", Quality: Excel.XlFixedFormatQuality.xlQualityStandard, OpenAfterPublish: true);
If you need to use tools as well, you could define a using alias for that:
using XLTools = Microsoft.Office.Tools.Excel;
and then use that alias to distinguish between the two.
However, if you don't need to use tools then, yes, I'd remove the assembly reference as Office interop is complicated enough!