Zand is correct to a point. Once you start the trader quest you CAN NOT ding 18 tell you finish the quest. Also yes you will have to do the trader quest to become an High elf inquisitor although I haven't seen a whole lot of diffance in the 2 diffrant types of clerics there are some spells and traits that would be more sutable for some players. Hope that helps.
it seems the inquisitor does a bit more dmage and the realy good diffrance is the spells past lv 20 have drfrent names with much the smae efect alowing trhem to stack wich is the same for all the other healers types and there good/bad conterparts