Robert. As a fully licensed Plumber Drainer & gasfitter, I am proud of my Proffession & extremely protective of it. You have asked for advice. As Plumbing has a direct impact on the Health of any Nation.
I would suggest that You particularly identify your question.
It is illegal for any person to carry out any Plumbing in most Countries, where that plumbing is contracting, the fact that some people believe that it is their God given right to delve into Plumbing, gives them the right to carry out Plumbing on their own house with the intention of selling the property, is tantamount to Contracting.
There have been too many accidents caused by unlicensed & handy man Plumbers. The health of your Family should be parramount & I therefore would suggest contacting A Plumbers Industry Assn in your area.
Regards – Bob from Australia