I suggested replace the whole kitchen facuset. It will be easier, however, you need some special tool to unscrew from the bottom, it took me two hours to do it (I was an ametaur), but after i got the tool, in minutes, I was able to do it. I won't bother replacing parts of the facuset. when you unscrew from the bottom, make sure water line are shut off.
To tell you the truth, kitchen, bathroom are easier to do, at least they are visible, things like shower facuset is the toughest because you can't see. Good luck!