Hey Ron -
We don't directly support the type of editing that you're after. As you've discovered, if you whack the first table you selected, you'll also lose all the associated tables.
The data source itself is expressed as XML, however. If you're handy with a text editor, you might be able to crack open the data source, and do a search and replace to substitute "Fact Table 1" with "Fact Table2". Make sure you do this on a COPY of your workbook, and keep in mind there is absolutely no documentation on this process - you'd have to do some reverse engineering on your own to get it done.
Hope this helps (a little).