I personally would do a full fluid exchange if it were mine...BUT I know many are gun shy and are hesitant to do that which I do understand, but at the very least I would do a drain and fill.

The way I look at any of the mechanical components that has fluids, especially a lubricate, it will be better the have new fluid over old fluid that has lost any of it's properties, would you ever not change your engine oil??

I say this over and over, there's no such thing as a lifetime lubricate, all lubricates lose some if not many of the lubricating properties the longer they are used in a friction/heat environment.

That all being said maybe you should take a sample of the transmission fluid and send it off to be tested, if it passes with flying colors, don't change it, if it fails then you will have to make the choice too do it or not.

I'm not sure if I have read of anyone having the transmission fluid tested but I think it's a good idea, it will answer many questions many here have on this subject, if you do this please post the results!!