We do have a local plumber we use for stuff so that’s a great idea. And to clarify do I need the ck-valve since the comment after said no? I’ll post a photo if it helps.If you have the same or near heater type, this should be an easy install.
Make sure there are Unions at the in and outbound plumbing lines of the heater. If not, then now is a good time to install them.
Next, do you have a check-valve btw the SWG and the heater? if not, then a Jandy ck-valve is something you should highly consider.
Finally, if your husband knows a reliable plumber, he could pay him to come inspect the job and certify if all specifications are met and all testing passes. This overcomes the DIY barrier of voiding warranty for a pure DIY install. If you can post a pic of your heater from the plumbing side, we can determine if you have unions and/or a ck-valve; just make sure the pic includes up to the SWG - good luck in the Garden State - tstex