Open System Preferences > Print & Scan > Print
Select the printer on the left then click - (minus)
Download and install new drivers.
Then go back to System Preferences > Print & Scan > Print
Click + to add the printer.
If you are looking for a replacement check this reference first http://support.apple.com/kb/HT3669
When reinstalling printer drivers you sometimes need to Trash the Manufacturer Folder from /Library/Printers so that the OS is forced to redownload the correct drivers