In this video I replace the flush valve and generally refresh all the internal parts and gaskets of a Mansfield toilet before reinstalling it using a rubber and foam toilet seal rather than an old school wax ring.
Here is the parts list for this project:
Flush Valve: https://www.homedepot.com/p/Everbilt-...
Tank to Bowl Kit: https://www.homedepot.com/p/Everbilt-...
Toilet Seal: https://www.homedepot.com/p/Fluidmast...
16" Braided hose: https://www.homedepot.com/p/3-8-in-Co...

I am also including the toilet fill valve that I replaced couple weeks earlier:
https://www.homedepot.com/p/Fluidmast...