a) One entry that allows users to service a printer, unjam it, and restart printer daemons on the machine print server?
Depends on the print server, I guess ...
b)One entry that allows users to kill jobs and reboot the machines in a student lab?
I'd be a bit cautios with the "kill jobs" though ... :) or are you talking
%users localhost=NOPASSWD: /usr/bin/kill, /sbin/reboot