I think what confused me was the instructions:
The reference to "old files" made me second guess myself. OK, I'll just go for it and put the folders up there. Thanks!
USPS RateV3 January 22, 2012
To install this code
1 go to your Zen Cart Admin to the Modules ... Shipping ...
2 Click on USPS and edit then save all your settings to NotePad as they will be lost
3 Click REMOVE to uninstall the current version of USPS
4 Load the new files with your FTP program they go in the same directories so you can copy the directory
to your server and overwrite the old files
5 Go to your Zen Cart Admin and to the Modules ... Shipping ...
6 Click on USPS shipping modules and click INSTALL
7 Configure your USPS shipping module
NOTE: this shipping module cannot work until USPS has updated their server with the new rates.
This should be done on January 22, 2012