If you really want the page header from Excel, you can create a PDF of
the page from Excel, then export the page from Acrobat to EPS or TIFF,
etc.
That will give you a graphic of the entire page, with good resolution.
If you don't have Acrobat, then there are alternatives.
You may wish to re-examine the need for the Excel header.
Obviously, when you cram an entire page from Excel into a Word page,
things (including text) may get scaled down.
Maybe that page needs to be a foldout, sized for the spreadsheet you're
trying to display?