The cabin air filter in my '98 Forester was under the glove compartment.
    Only a couple of screws to remove. In my '03 you have to remove the
glove compartment to get at it.

Instructions and some drawings can be found at www.cars101.com

Not all soobs have the filter installed, but I think they are all (from
the late 90s ?) built with the capacity to receive a filter. Some folks
build their own filters out of household A/C filters. If you want to
purchase soob cabin filters, price them from an online discount dealer
(I've had good luck from www,subarugenuineparts.com - there are others)
OR, make your local dealer match the online price.

Carl