I do NOT think you will get much debate, adding a cooler will be wise. Check your local auto parts store, adding a tranny cooler is normally a pretty easy DIY adventure.
Of course, you will get the debate on whether or not it should be run seperate of the exiting cooler, or in conjunction with the existing. :B BEFORE or AFTER :h
I go with "in Conjunction". I also prefer adding the new cooler BEFORE the existing one in the radiator. This "Helps" the existing, while still allowing the existing to do its job. Up here in the colder states, we need that warm fluid in winter time.