After the class change the Fighter becomes a Knight, the Thief becomes a Ninja, the Black Belt becomes a Master, and the Red, White & Black Mages become Wizards. Knights and Ninjas can now use low-level magic, the Wizards can learn some more spells, and everyone can equip more weapons & armor, except the Master who is exactly the f---ing same as the Black Belt.
You should head back to the early towns to pick up some spells. Knights should grab CURE & CUR2, Ninjas should get stuff like SLEP, FIR2, LIT2, FAST, & ICE2, and the Wizards should pick up WARP & EXIT.
Now to get down to the business at hand, you need to go to the Carvan.
On my you're heading to the Waterfall so get going.