Finding and replacing text in headers is a common task in Excel. There are a few different ways to do this, depending on what you're looking for. Here's a quick rundown of how to find and replace text in headers in Excel.
The first method is to use the Find and Replace feature. This can be found under the Home tab, in the Editing group. Simply click on the Find & Select button, and then choose Replace. In the Find What field, enter the text you want to find. In the Replace With, enter the text you want to replace it with. Then click on the Replace All. This will replace all instances of the text you're looking for, throughout the entire workbook.
(The dialog box shown above appears when you click on the "Options >>" button while performing a search)
(The dialog box shown above appears when you click on the "Format >>" button while performing a search)