Remove the front bezel by pulling it straight off - carefull not to break those @#$%^&* plastic clips at the 4 corners, or you're pwned. I've had good luck grabbing the entire bezel at the top and bottom (not the sides), but I cringe each time I go near it. Once that's off, you should see the filter cage locks into the front of the chassis with some L-tabs [look inside the case to see if yours face up or down]. Slide the filter cage to disengage the L-tabs, and it comes right off.
The filter element is open cell foam - you can wash it with plain water under the tap and blot it dry between 2 layers of a towel by pressing against a table or counter. Wave it a few times to give it a final air dry, and put it all back together.