My 1999 sebring I just purchased has dark brown transmission fluid instead of red. When I asked the previous owner she said she had just never had it changed. Can never having it changed cause it to turn brown or is it a sign of the transmission going out?

that'll do it - it's a 5 year old car with no tranny fluid change, it's not likely it would still be red. She didn't know any better, but now you do - so change it now : )

It's just like any fluid, it deteriorates over time. They are making the fluids better now, and supposedly some will last until 100k, but I don't trust it.

Most people think they are taking good care of their car if they change the oil every 3k (change the coolant too if she didn't do that regularly). I don't necessary suggest a tranny fluid flush, esp if you diy (and do it every 2 years). Just drain and fill (and replace the filter) - regardless of the car, you usually end up with 1 - 2 quarts that don't come out when draining, but all of the really bad stuff is on the magnets in the pan anyway.