Secondary Proffesion?

I know on Nightfall I can change secondary class later in the game. But... on the Prophecy, the NPC tells me that it's perm. Is it possible to change secondary class later in the game on Prophecy?

yes in the desert one you ascend, there wll be different npcs giving out quests that you can do to change

Yes, although it is much later in the game.

The truth is that changing secondary professions has become easier for character of later campaigns. In order of difficulty from easiest to harder :

1. Nightfall
2. Factions
3. Prophecies

with Prophecies being the hardest and way later in the story line. I would suggest that you build a character in Nightfall buy the ability to change all the secondary professions and then go back and do the other campaigns.

If you like PvE quests and don't like spending PvE gold when you don't have to, go with the changes for the core professions in Prophecies. It takes a while to get there compared to the other chapters, yes, but you get to do quests to learn four to six (depending on your original professions) new secondaries. It does take longer, but questing for such things always felt less ... dirty and cheap to me.

Follow ermns advice above if you just want it fast.