You know someone knows what they don’t know, when their question looks like the TOC of a multi-page tutorial! 
Will your WordPress site continue to exist, or are you redirecting one domain to another?
This portion is ensuring nginx reloads when the cert is renewed, and of course pointing to where the certs are saved. But that is fairly standard, and really the an initial edit and done. It is likely a cron job. For mage party here is how we load the certs for prosody, taking from that homebrewserver tutorial:
0 4 0 * 0 /usr/bin/certbot renew --renew-hook "prosodyctl --root cert import /etc/letsencrypt/live" --quiet
Something similar for nginx will work.
Getting a new cert is a 30 second process. If you set your DNS up (like using a “liveDNS” service or having a low TTL), you’ll be able to move it over with about 5 minutes downtime, at most. But don’t trip, your site ain’t that important to the web. It could disappear for a whole 10 minutes without anyone calling the authorities.
Keep in mind, Let’s Encrypt’s model is literally: can you prove you control domain? Okay, you get a cert!
Another query that I’m not sure I’ve handled myself is running the renewal for multiple domains. I think it probably still works, but can you put them all in on pem and reference them that way? Hmmm. 
Also, in case you are planning to redirect from hitlonde to citracode, I actually recommend leaving hithlonde resolving to DreamHost. If that’s the case, let me know!