simple question, do I need to update the RSA cert to an ECDSA cert?
Or does it do it automatically now?
Or do I do it with certbot certonly and then it's ok.
In short: No; You are not required to change anything - nor will any such change happen automatically.
That being said... [Enter the long story]: Apache does support using multiple certs [of different types].
So, you could actually use both [an RSA & an ECDSA cert] for your domain [in the same vhost].
You could also review the differences [pros and cons] of each type and make your own educated decision about which type/strength/ciphers you want to use.