BMW Repair: bmw 1996 318i 4 door, slick 50 oil, urban myth

Question
Hi, you are pretty rare so I'm happy I found you.  I recently purchased a 1996 BMW 4 door 318i and it's in really good shape.  I purchased it from my brother in law who was the only owner and drove it on the highway for his 2 hour commute every day.  It has 175k miles on it and I love it and it runs great.  
Since I purchased it, every couple of gas fill ups, I've been putting gas treatment in the tank.  I've changed the oil and used slick 50 oil additive in it.  I'm trying real hard to take care of the car.  
The next thing I want to do is change and flush the transmission fluid.  It's automatic and changes gears smoothly but by brother in law doesn't remember changing the transmission fluid and even if he did, I figure, it can only help right?  Wrong is what I heard.  I keep hearing that if I have no problems with the tranny, then I shouldn't change it.  Someone told me they bought and old Ford and everything was fine until they thought what I thought...that it could only help to change the transmission fluid and after they did, they ended up needing a new transmission.  
How can this be??  How can it even be a rumor?  Fresh, clean transmission fluid can only help. Plus, I'll have the chance to add a transmission additive like slick 50 or something.  
Have you heard this rumor before?  Is it an urban myth?  What do you think?  What does BMW suggest?  I'm really confused because all I want to do is take care of this car and all I want is for it to last me a long time.  Please help...should I change the transmission fluid???????
Thanks.
Emad

Answer
Well I hope I can help with the confusion your having about servicing your tranny.I too often wonder what would be the right thing to do.I would first look at the owners manual,you have purchased it from your brother so hopefully it is still there.Some BMW's unfortunately do not have this option,if you have a dip stick you can change it but if there is no dipstick it is considered a lifetime fluid.(Which I don't understand because there is no way of putting fluid in if you had a seal leak !.)So check to see if there is a dipstick for the transmission first,if there is one I'd service the tranny if not I hope it shifts well for you because the only repair is replacement.