I've got a '97 model and I see the manual suggests replacing the ventilation system dust filter, recirc filter and activated-charcoal filter every two years. That seems to imply there are three units, but the shop says there is only one large (not only in size, but $$$..) filter unit to replace. True?

Some 140 do not have the activate charcoal filter, if the hood near the wiper is smooth, flat, and do not have louver. Then, you'll need to change the blower filer under the hood on the right side, and the filter under the glove box. These two filters are cheap.

jack