My 99 Eldorado has about 70 k miles down, I strongly assume the previous owner (I bought it at about 63 k) never changed the cabin air filter. I just read an article in the paper that one should change it every 10 k miles or so. Anybody ever done this?

How does one change it, and how much would a new filter cost? Can I get one at a store like Autozone or do I have to get it via the dealer?

Cabin air filter needs to be checked from time to time, to see if there is a need for it to be replaced. There are plenty of car parts (http://www.autopartsdeal.com/) stores where to find these. Though I am not sure how much this costs, its been a while since I changed mine.

I don't know about cost but from what I've read there a PITA to change.

good luck replace it
as the Eldo doesnt have an air cabin filter...