I did the DIY flush on our Aveos a few years ago, see here: http://www.aveoforum.com/forum/f94/a...d-flush-16317/
Was the best thing for them, have had no issues at all some 30K+ miles ago.
Very easy job for anyone mechanical, your tranny will be ever thankful to get all that crap out of the fluid. So if you can get the full flush or do it yourself you won't be disappointed. Trans will shift smoother and run more efficiently, I would recommend a new filter as well, even though it is probably fine still.