I have a 2000 Camry and before that I had a 1997 Camry.  There is a 1
year time change recommendation for the transmission fluid.  It suggests
a "refresh" rather than the dealership full flush unless there is a
major problem.  You do have a major problem,  however you might try
refresh.  If it were my car I would drain the transmission and refill it
with the Dexron-3,  wait a week or a month and do it again.  If the new
fluid cleans it up and frees the gummed up clutches and valves you have
it cheap.  Then the second refresh is to get rid of most of the crud.
There are a lot of places inside that will not drain like in the lower
part of the torque converter and the valve body,  but most of the fluid
will have been replaced.  You can buy a kit of seals and pull the bottom
panel of the case and clean or maybe replace the filter (screen?) also.
 My cars  get Mobil-1 ATF (synthetic automatic transmission fluid)
instead of Dexron.  The synthetic will hold up better to heat and last
longer.  I still refresh it every fall.  The viscosity of each fluid
will be very slightly different but not enough to make any difference.
These fluids are engineered to be interchangeable and mixable anyway and
the mechanical parts of the cars are engineered to do well with anything
generally available for cars  unless noted on the packaging.  There is a
"Ford F"  fluid that is only for specified transmissions.  And there are
special fluids for things like airplanes that do not mix with anything
else or other brands,  of course,  but that should not be a
consideration for most of us. Location of the drain plug and replacement
amounts are in your owners manual or repair manual from the auto parts
store of your choice.