Changing LNB on sky dish

We've taken the plunge and cancelled Sky TV. We had the Sky Q package with multiroom so will be sending the equipment back.
As I understand it to be able to watch Freeview channels again on our old Sky HD boxes I need to swap the Sky Q LNB for a quad LNB.
They look cheap enough on Amazon but has anyone any experience in swapping them over?
Is it a simple enough job to do?

Any help/advice would be appreciated.
Thanks