Replacing a data source does so for the whole workbook.
If I understand correctly, you have multiple sheets, and you want to replace the data source for only one of those sheets.
If so, do this:
Make a copy of your workbook.
Do REPLACE DATA SOURCE in the copy.
In your original, delete the sheet you want to have a new data source.
In the copy workbook, right-click on the tab for the sheet you want to change. Click "Copy".
In your original workbook, right click on any tab and choose PASTE. This will paste the sheet from the copy-file into your original workbook. It will bring the new data source with that copy. This will leave all the other sheets alone.
Thank you! That's a neat trick