Droplet migration

Scenario:

• we have a website hosted with DO for the past 7 years and in those 7 years we did exactly 0 updates to Ubuntu, Apache, php, …
• at this point we are running Ubuntu 14, php 5.6, … and we would like to update everything (to Ubuntu 20, php at least 7.4, …)

We figure to best way to update everything right now would be to create a new Droplet from scratch, set it up, migrate the files there, test everything out and when ready - “somehow” switch the current Droplet with the new one.

Here’s the idea we have so far and I’d like to know if this is doable or not:

• 1-click install a new Droplet https://marketplace.digitalocean.com/apps/lamp
• migrate files to new Droplet but keep DB pointed to the old (current) one
• test everything out on the new Droplet
• once ready, put everything in maintenance mode and migrate the DB to the new Droplet
• (and here’s the crucial part) repoint users to this new Droplet – how would we do this?

Since we already have everything we need in our account - could we just go to => Networking > Domains and repoint the IPs from the old Droplet to the new one? Would this work? Would this need time to propagate or would it be immediate? I’m guessing we’d need to rekey the SSL certificates after we’re done?

Thanks!