Plex migration question

I’ve just purchaed a WD EX2 device (I’m new to NAS devices). I have a Plex server installed on my Macbook, primarily for a very large music library. I understand that it will be relatively straightforward to install a new Plex server on the NAS drive, and run Plex from there, which will be more convenient. What I’m not sure about - and forgive me if this is a stupid question - is what I should do with the old, original Plex server. Will it be automatically replaced (it will be on the same network, obviously) or does it have to be manually uninstalled? Thanks for your help!

Not sure what you are trying to do.

It is VERY possible to use multiple plex servers.
You can select which plex server you are drawing data from in the plex player app.

It is VERY possible to have multiple plex servers access the SAME media files. I have done this in the past, with one server on my PC pointed to the NAS for media; and the NAS itself running an instance of plex media server using the same NAS files as the library source.