Wanting to change Trading Class but Dunno how

There is an npc that wipes your trading skill so you can start a new one. I think it can be found in the capital cities.

 

Afaik they can only change it to Alchemy or Spellcrafting, at least that was the case with my char

 

Hopefully this is what you were after, skillfully stolen from here

"Persons who have already chosen a “mundane” trade specialization (armorcrafting, tailoring, etc.) may not train in Spellcrafting or Alchemy. There are quests available for the “clearing” of one's trade specialization so that current trades characters may choose to begin Spellcrafting/Alchemy; however if that is done the characters’ current tradeskills are all reset to 0. The reverse is also true: once a character specializes in a "magical" tradeskill (spellcrafting/alchemy) they cannot gain any skill in "mundane" trades. To do so, please consult the following august personages in your realm's capital city:

Albion – Edie Wharton
Hibernia – Fabrice
Midgard – Gudmund

Spellcrafting is available to “pure casters” as well as healers (basically, any class that cannot specialize in a weapon). Specifically:

Albion: Cabalists, Clerics, Sorcerers, Theurgists, Wizards
Hibernia: Druids, Eldritches, Enchanters, Mentalists
Midgard: Healers, Runemasters, Shamans, Spiritmasters

Alchemy may be taken up by “hybrids”, or fighting classes that have some form of magical or roguish bent. To wit:

Albion: Friars, Infiltrators, Minstrels, Paladins, Scouts
Hibernia: Bards, Champions, Nightshades, Rangers, Wardens
Midgard: Hunters, Shadowblades, Skalds, Thanes"
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Hope this helps

 

I really love your signature. Or is that, Jesus, wtf is that thing and why does it take up my entire screen.