Actually, setting up LE on FBSD was even easier than that. We've had LE working on two of our FBSD servers for 4 months. Running the py27-letsencrypt client with --certonly and -d domainname -d ..., installed the certs in /usr/local/etc/letsencrypt/live/<domain>/...
Then pointing nginx to the "live" cert location and setting a cron job to renew every 4 weeks or so pretty much takes care of the whole process. I notice the FBSD LE client was just upgraded, not sure what new features it offers, but certainly should work at least as well as before.