The hole that part is in is most likely filled with splooge. Spray some brake clean, WD40 or anything to work the piece out. You can even twist and turn it with some pliers. Just be careful and wrap the end with a towel or some tape or something.
You have the two side valves out right?
Spray in here. The last bit of the shaft is covered in gunk so it wont pull out cleanly. The spray cleaner will help.