if you have burnt brown fluid, a flush will kill your tranny. like it wont leave the shop dead.

you should only drop the pan, and change the filter. thats is, then top off with 8 qts of new fluid.

if the shop is any good they wont do the flush to your car when you have hi miles or bad looking fluid, they will make you sign a waver if they do flush it. if they feel the fluid is old or burnt up.