For me, the things you should review before the transition are:
1.- The big difference between a certificate issued by Let's Encrypt and your current certificate could be the validity, Let's Encrypt certificates are valid for 90 days and maybe your current certificate is valid for 1 year so you should renew the certificate more often, ideally every 60 days so in case there is any problem you have 30 days to solve it.
2.- As Let's Encrypt certificates are valid for 90 days you should found a way to automate the process (renew the certificate and reload the services using it) without manual intervention (and that is one of the reasons LE certs are valid for 90 days, to force users to automate it).
3.- You should think how you will validate your domain to get a certificate, there are 3 types of challenges (http, tls-alpn and dns) so depending on your needs or the services you are using then you should know which one you will choose.
4.- What is the acme client you will use to get the certificates? There are tons of clients (the official one is certbot) so depending on your needs you should use one or another client. Once you choose the right client you should learn how it works, how to issue a cert using it, how to renew the certificate, how to reload the services with that client and so on.
5.- Test, test and test and once you are confident with the process, go ahead and switch to Let's Encrypt