New owner. Off line chlorinator question.

[tkim6599]

This where water line goes into the chlorinator.



This is where it feeds out.




I'm trying to figure out if replacing it with a Rainbow in line chlorinator is easy enough for me to do, or do I need to call the pool people to install. I'm a little leery of doing so, since they were the ones who installed the chlorinator this way in the first place.

I can see replacing the connection between the pump and filter since there was a hole drilled into it to install the venturi scoop, but what about the hole that was drilled into the return line? do I plug it with something?