More than likely, if SSH was working and now it's not AND it is no longer listening, then (more than likely), you do NOT need to reboot. You either need to get to the console (non SSH), log a ticket with Support with your hosting provider, or have someone console the system for you. I suspect that SSH might be hung and just needs to be restarted (sometimes you might have to kill the old ssh PID to get the restart to work, depending how bad SSH hangs - and if that doens't work, you might have to remove the SSH lock file if things really get into hand). With Linux distros, it's rare you reboot because of a software issue - theres usually many ways around it by use of command line tools.
If there is a remote reboot option, I don't recommend it, however, if it's your only way, use at your own risk.