Immediate step(s) after SSL upgrade?

i’m considering soon ordering an SSL for my domain/website where I have a WP site, and just really nervous about this SSL upgrade. I am afraid that my WP site will not load immediately after the web-host finishes installing the SSL. And I’m also concerned that the SSL installation will finish, I will attempt to change the https:// to https:// , and then all of a sudden, the plugin either doesn’t work, or for some reason, my site just does not load. So, after my hosts finishes installing the SSL on my website, do I need to immediately log-in to my WordPress Admin Panel at

https://example.com/wp-admin

and do the change that this article says:

https://designmodo.com/wordpress-https/

On the part of the page that says, “Configuring WordPress for SSL/HTTPS”? Do I need to do that first, and then secondly, also, run a plugin like “better search replace” to change all of the https://example.com to https://example.com in my site? Do I need to do both of these steps? In what order should I do them?

Also, how will I be able to login at my https://example.com/wp-admin like normal, if my website is going to be down after the SSL activation is complete since, at that point, I will have not made any https://example.com to https://exmaple.com changes yet? Will I be able to access my admin panel to do these two steps?