Good questions!

Yes, you would switch to a leather worker and creating items with that tool would earn you experience points. Leves are divided in two groups, Regional and local Leves. Local Leves would be the ones for DoH classes. I believe with the last patch, creating regular items yields large ammounts of exp points based on the quality of the item you create, go ahead and try that out!. For a good income starting the game, I would advise leveling a Disciple of the Land class (DoL).

Side Note: I'm at work now and not much to do xD