I don't think a dealer would change it. They only know how to replace the ENTIRE trans, not do services. You should look for a ZF service center near you(IF they even have them in the states?). Maybe you can find a good indi near you.
These guys in Cali seem fairly knowledgeable. Plus their prices on the ZF lifeguard fluid is really decent.
http://www.thectsc.com/index.php?p=c...&parent=7&pg=1
Dack