Broke nubs off of stem when cleaning

I took the bottom parts out. This can basically be done without tools. You need a phillips to unscrew 3 screws to remove the stem. Then easily replace with the new one. Putting the spiny washing part was kinda weird because I was afraid to break the nubs off again. I took the whole bottom carriage out so I could see better, pushed down kinda hard and twisted the right way (figure out which way needs to be twisted before hand by looking through the bottom of the stem).