I believe that the dealer was referring to air filter. Ask the dealer
to be sure. If it's air filter, I had learned that with most cars, it
is soemthing you can do.
When I did it on my Nissan 2 years ago, even though I knew that I could
change it myself (or ask someone to do it for 10/20 bucks for labor to
put the filter), I couldn't buy the air filter (it was hepa) from the
auto supply store and that only dealers would sell it. So I did it at
the dealer for 80. Recently, I learned that you can just buy ANY filter
you desire, cut (and shape it if necessary) and put it yourself. Some
suggested to get it from Walmart.
As far as I know, micron filtration and hepa filtration are top of the
filtration process. I lerned those when i was purcahsing a canister
vacuum cleaner 6 years ago.My kowledge may be out of date.
I will never let the dealer put an air filter for me again.