"Or would it be necessary to purchase another printer to maintain what level of autonomy there is?"

Enabling file and print sharing is not necessarily a security risk on the network. Don't share any files on the host computer and you should be relatively safe. Spyware doesn't jump from computer to computer such as worms or other virus's.

Active scanning for spyware is now a component of most Security packages. The key issue is in maintaining up to date definitions.