Everything that I have read is to not drop the pan to replace the
internal filter. That filter is nothing more then a screen. The problem
is that it can be very difficult to reseal the pan without it leaking.
I have been told that starting in '98, Subaru added a spin on filter. I
haven't seen it, but it looks like an oil filter. That should be easy
to replace. Filter is prolly down very low on a frame rail under the
car. Follow the fluid lines back from the radiator cooler to find the
spin on filter.
Suggest changing the ATF by removing the drain plug on the bottom of
the trany. That will drain about 5 quarts out of about 10 quart system
capacity. You can also take your car to a quick change oil shop, many
of those have a machine that will remove all the old fluid from the
trany. Cost at my local Jiffy Lube was $175 for the job.