'''Only Apple can do a home button swap.''' If you replace yours using 3rd-party parts, it deactivates the button and turns on assistive touch. Therefore this procedure is only useful as part of a display assembly replacement, where the home/Touch ID sensor must be transferred from the old display to the new one.
Follow the steps in this guide to remove or transfer the home/Touch ID sensor assembly, including the gasket and cable, in your iPhone 7 Plus. To avoid accidentally straining or tearing the display cables, it's best to completely detach the display assembly before beginning repairs on the home/Touch ID sensor. But if you are comfortable doing so, you may skip the display assembly section of this guide and go straight to the home/Touch ID sensor section.