It couldn't be simpler...
Remove the head discharge fitting, remove the joker valve, put the new valve in, replace the head discharge fitting. Just be sure you don't overtighten the fitting when you put it back, 'cuz the flange on the joker valve is also the gasket between the pump and the fitting. It'll leak if it's over-tightened. As long as you're doing toilet maintenance, now would also be good a time to lubricatate properly. You'll also find instructions for doing that in my book.