Actually pretty simple to remove.
The white trim ring snaps off. You will see a metal ring with machine screws. Screws come out, ring comes inward and the other half of the port is on the outside. Flat putty knife to gently work the sealant loose, maybe some inside and outside effort and it will come loose.
I replaced all the Beckson plastic ports on our previous boat a Catalina 34 with these. They go in and out very easily.
We had a couple on our brand new 2008 Hunter 38 that leaked because the factory got stingy with the sealant. So when you reinstall them be sure to get generous application of it. Probably a two person job to out back in. One to hold outside so it doesn't slide around and the other putting the screws back in the inside ring.