The "STAR" is a magazine published for members of THE MERCEDES CLUB OF AMERICA. THe articles are well done and range from car features to technical issues. There is a Tech Forum, not as nice as this, but pretty good. It is open to members of the "club" If you contact them they might send you a comp. sample of the magazine. It is a national, but have local clubs that have functions on a regular basis, dinners, trips, etc.
http://www.mbca.org or 800-637-2360

The interior filter is just a thin piece of foam rubber, very easy!
The air filter is in the engine compartment in the top, also easy!
The "charcoal" sits in the heater assembly, and needs vacum supplied to a little port to collapse the rubber seal around it so it can be pulled up and out. When you remove the wiper trans mission it is under it