If the fluid is discolor.. it means the the bans are burnt up and/or the clutch plates are bad.. would slip though if bad plates..
time for a change, and filter ASAP, so long as its not burnt. If it is (it'll smell strongly) burnt, that means your clutches are more than likely slipping, which really isn't good news.
I would Just drop the pan and change the filter (Every 30-40K).. Just like the oil filter.. Gets dirty right>?? would you leave that oil filter in the car that long? or let if get so dirty ??
yes make sure you do get the old fluid in a pan because you need to know what came out!! Never put to much or not enough trans fluid back in.
NEED Trans fluid, gasket and filter!
Get about 1 to 2 gallon of trans fluid. (you can bring about one if you don't use it!) and ask Auto store or look up Spec meeting fluid so you don't ****ed shit up lol.
Jack car up, (jack stand on each side) start by removing one end of the pan so you can drain the fluid in the empty pan. (take your TIME)
once you get the pan off look for debris one the magnets.. if a lot is on there that may be a bad sign! (internal damage)
Next pop out the filter, replace, (clean pan "the in side of it with crab or brake cleaner" and wipe dry)
Next once you cleaned pan and pop in the new filter.. put gasket on (new one) and re-install the pan.. "torch to Spec" anyone know the torch spec?
if not make sure you get them tight!
Now you want to put the fluid that came out of the trans into old oil jugs or anything you can measure how much you have there...
Then open fill plug and fill up what you have measured form old fluid..
and your good... No need for a Fush!!!
If its burnt ... have a trans shop have a look that may have you use a additive... as in "Lucas Transmission stop slip" which and also rejuvenate old worn trans fluid!!