This is a really good question that may not have a good answer!
The answer, unfortunately, may depend on symptoms that only occur when you
attempt an install, and something does not go right.
Ill behaved print monitor modules can cause conflicts. (And it may be the
new or old module that is the culprit) Generally, the applications are ok
to leave alone, with the understanding that some will not work, or not work
correctly with the new printer. Uninstalling an old printer may or may not
remove all the registry entries and alterations. This is more commonly found
with all-in-one printers, or printers that have some sort of "legacy" driver
scheme. Usually the fax/scan side is impacted the most. USB printers
occasionally have conflicts with schemes that setup virtual ports. The
virtual port schemes came about because some of the first generation USB
printer drivers installed multiple copies, one for each USB port. If done
properly, the virtual port schemes can also facilitate LAN use with ethernet
or wireless print servers. Sloppy virtual port schemes can cause all sorts
of difficulties and compatability problems.
Common practice is to install the new printer driver and printer, make sure
the printer works properly, and then think about uninstalling the old
printer drivers. Some of the older printer driver packages would install
correctly only on the first USB port, and may force default selecton of the
newly installed printer. This default selection may reoccur after every
reboot. (Not good when you are adding rather than replacing a printer)
Installing the newest printer from a company is safer than reinstalling an
older printer and driver over a newer printer and driver. (Sometimes the old
driver install will replace modules with obsolete ones that are common to
both.)
Personally, at home, I usually leave the old drivers, since the old printer
is usually available as a backup. There is nothing like running out of ink,
discovering that spare ink for the new printer is depleted, and the stores
are closed or out of stock. (And you have a deadline to meet.)
