This Bosch site describes the process (click at the bottom of the page 'vehicle specific information') http://aa.bosch.de/advastaboschaa/Product.jsp?prod_id=91&ccat_id=37&language=en-GB&mtype=P&publication=1&flash=
It is about a 20-30 minute job. FastLane carries the filters. The generic ones are plain dust filters - the Bosch can be had as dust and odor paper and charcoal filters for more money - call Phil and specify the charcoal filters if you want organic pollutant and smog control as well as dust and pollen. The Bosch page is sometimes a little tweaky to open. Basically it says you remove a flat panel under the glove compartment to clear access to a plate on the passenger side of the trans tunnel. Two grooved slides on tracks are moved so the filter can be rotated/pulled down and out. The Bosch site has pics and descriptions. Pretty simple job after you have done it once or twice.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E