It's staked to prevent movement upwards but a punch in the correct direction (which direction is correct I don't remember - Google WILL give you the answer). There is a trick to it, some good YouTube videos on the removal. Not hard just a little trick I can't remember.
Good luck, you'll get it.
Edit: Here's one I found when I changed out mine. Took seconds after I saw it:
h ttp://www.youtube.com/watch?v=92FiYzxdy2A