Thanks to Maureen for this info:
To get the header there is a button on right hand side of the upper screen, above the date/time of the email that says Standard Header and then there is a down arrow. If they click on the down arrow they can choose Full Header. It will pop up in another box so they will have to copy and paste it into a word processing package even better just into Notepad (Start>All Programs>Accessories) so it doesn't add any code on to it.
Log in to Gmail.
Open the message you'd like to view headers for.
Click the down arrow next to Reply, at the top-right of the message pane.
Select Show original.
The full headers will appear in a new window.