Taking an object requires a DC 20 Sleight of Hand check, followed by an opposed Spot check on the pickpocketee's part against the result of the Sleight of Hand check. They get the Spot whether your SoH check succeeds or not. The PHB and Rules Compendium don't say anything about modifiers to...
Actually, for spell trigger items the spell just has to be on your spell list, you do not even have to be of a level to cast it yet. You do have to know what spell it is, though. The "as if you were a wizard of level X" part kicks in with staffs when X > the staff's level, as staffs allow you...