I got ready to change the fluid in this 2004 santa fe. The parts store told me computer says service at dealer only. I'm curious if this is something I shouldn't touch? The transmission desperately needs changed. Looks like muddy water, car has 300k miles and I'm assuming hasn't been changed in a LONG while. Thankfully no metallic bits in the fluid just super dirty. So is this something I can change or does it absolutely need done by a dealer? If so why does it need done by a dealer?

 

The vehicle uses a special tranny fluid
If you use the wrong one you could potentially destroy the tranny