Is it possible to retain the tables and dashboard design you create but later update the data file (Excel sheet) associated and upload with new information (i.e. New data AND revisions to the old data)?
Yes, the tables and dashboard design can be retained with updated information later on.
Save the Tableau project to the Tableau public server
Open Tableau Desktop Public, File-> Open -> From Tableau Public… open your saved Tableau project on the Tableau public server
If there is any updates to your data, go to Data source connection interface, Edit Connection… reconnect to the updated Excel file. The newly added columns and rows will be updated in the Tableau project while the original Tableau work will be retained.