Interesting (and confusing!) topic.
First you need to know if your car is equipped with the charcoal filter system.
It used to be on the older 140's you could tell by looking at the hood, it had the "slots" running across the back part of the hood, the non-charcoal had no slots, just a flat steel hood. Later they must have decided the slots were "cool" as they put the slotted hood on all models, charcoal or not. The best way to tell for sure is to look for the charcoal switch on the dash, maybe someone can post a picture of what the emblem looks like, or check your owners manual.
WITH charcoal filter system, you have the following filters
*recirculation filter, costs more like 10 bucks, even at a dealer. It's underneath the dash on the passengers side, kind of a trick to remove it.
*charcoal system pre-filter, costs a couple hundred bucks, maybe less now, it's in the underhood area above the blower motor.
*charcoal filter, costs, last time I had to replace one, $466 at a dealer. It's in the dead center of the firewall. The wiper system needs to be removed along with the rain tray, then a vacuum pump is used to "deflate" one of it's seals so it can be removed, very tricky.
On the life of these things, I believe its recirc filter every 15,000 miles, charcoal prefilter every 45,000 miles, charcoal filter every 75,000 miles.
WITHOUT charcoal there is only 2 filters:
*recirculation filter same as above
*dust filter, costs I think $20, we don't see many 140's without the charcoal system. It's the same shape and location as the charcoal pre-filter noted above, but is a simple paper element, the charcoal prefilter does have a charcoal covering on the botton part of it. Also the normal dust filter has a hard plastic frame around the element and the charcoal pre-filter is like a rubber frame. If you are sensitive to pollen and so forth I would think a "poor mans" charcoal system could be created by replacing a dust filter with the charcoal pre-filter, assuming your 140 doesn't have the charcoal system.
I believe the service interval on a non-charcoal system is to do both every 15,000 miles.