There is no drain plug on the Tranny pan. The most common method to drain the old fluid is to drop the pan. I have heard that is to "encourage" you to change the filter at the same time. It IS a good idea. You CAN tap the pan and install a plug the first time you drop it. (I wouldn't. Changing tranny fluid is not like changing oil. You might do it twice during the time you own it.)
I do lots of stuff myself, but was convinced to do a real "flush". It involved circulating new fluid under pressure for 10 minutes or so, draining that out and doing one final fill with brand new fluid. It made a HUGE difference! Normal cost is around $60 - $65 but I thought it was worth it. Doing several changes to "clean it out good" is going to add up. Tranny fluid is quite a bit more than oil (non-synth).
BE REAL CAREFUL about type of fluid. I have a '96 V8 and the Ford website gave me a different answer than my local dealer. (No, I did NOT let the dealer do the flush!

)