I currently have the older letsencrypt installed on a Ubuntu 16.04 server running apache. I’d like to upgrade to the newer certbot.
Can I simply follow these instructions to make the switch? I’m assuming that, since I already have the certificates created for my domain and apache is already configured that I shouldn’t run the sudo certbot --apache or sudo certbot --apache certonly commands in those instructions. Is that correct?
Also, I currently have a cron job (/usr/bin/letsencrypt renew) for auto-renewing my certs with letsencrypt. Once I install certbot, I can remove that job since certbot runs its own renew check, correct?
That's right. Upgrading won't erase your certificates or configuration, and everything should keep working as before.
Yes. The Certbot package includes a systemd timer and cron job. (The latter will disable itself since you're using systemd.)
If your current cron job includes other options (like a hook to reload a mail server) you'll have to do something about configuring that, though.
For what it's worth, the Certbot package keeps /usr/bin/letsencrypt. (Replacing it with a symlink to /usr/bin/certbot.) So you can start running "certbot", but your old "letsencrypt" workflow won't stop working.
You can run "certbot renew --dry-run" to test renewing still works.