1) Disarm?? Not sure that there is a combat action in the book that defines this, but there is a spell that would do it - Bladeshattering. But if you were needing to create a house rule, I'd suggest the Grab combat action and then perhaps an opposed Strength test. If you were wanting to attack the enemy's weapon directly with your own, then the GM should come up with a TN and a DOS that will have a desired effect. Lastly, you can just use the vague system of Extraordinary successes to achieve a Disarm.
2) Shield Bash would be done by taking the shield as a specialized weapon choice (i.e. Armed Combat: Clubs (Shield) ). The shield then may be used as a weapon or a parrying device, although if being used to parry with, I would not extend the Parry Bonus normally extended by a shield.