How can make changes to my smb.conf file go live without a reboot?
Solution 1:
Restarting just the service seems like an improvement on rebooting. Even better still is to make use of the config reload that comes with many linux services, including Samba. This feature is often accessed with a SIGHUP signal or via a control program.
Use smbcontrol (man page) to reload the config with the lowest downtime and lowest-possible impact on services already using your shares. So, just run this:
smbcontrol smbd reload-config
Solution 2:
You have the name of the service wrong. Try:
# systemctl restart smb.service
# systemctl restart nmb.service