Where do you change you're secondary profession?

I know there is a place to change your secondary profession, any1 know where it is and how to do it?

In the Crystal Desert, after you have ascended, goto the following places and see the ghost for the quest related to the profession you want to change to. Do the quest and see them again to confirm you want to change.

Heroes' Audience
Cembrien: The Elementalist's Path
Zratha Kor: The Necromancer's Path

Seeker's Passage
Nausuan: The Monk's Path
Telius: The Ranger's Path

Destiny's Gorge:
Eulenias: The Mesmer's Path
Agastos the Brave: The Warrior's Path

you're --> your

Can you switch as many times as you wish, or can you only change once?

As many times as you wish after you have completed their quest. And you don't completely lose the skills of the profession that you're changing from. That is, if you change back to a previous profession, those skills will return.

And once you have completed each "path" quest, you can go back to any of those people to switch to any secondary you have unlocked. You don't have to go back to that particular person.

Whenever I switch secondaries, I alwasy go to Seeker's passage because you warp in right next to the person.

Just a note that you need to talk to Vanyi in Droknar's Forge after you ascend. You can find her near storage.
She will ask you to travel to the 3 cities mentioned above by "Caged Fury"
Once you start going to each city you will then go talk to her and then you can do the quests for each profession.