I would like to know whether an updated print driver has successfully replaced a previously installed driver.
Easy. Start up the CUPS page (127.0.0.1:631 in the browser) and locate your printer, there should be a line that shows the driver.
This is what the driver for my LAN printer says:
Driver: HP DeskJet 520 - CUPS+Gutenprint v5.2.7 (grayscale, 2-sided printing)
Once you do a system update (Ubuntu I guess : apt-get update
if I'm not mistaken) the driver (usually) gets a once-over as well...
Oh, and, by the way, it is not the printer that replaces the driver, but the system that updates/replaces the driver for the printer, just a detail...
EDIT : make sure you have the GutenPrint cluster installed, it has the drivers you need, I'm sure...