just tell them you are hearing a clunking noise, that is either coming from the rear diff or tranny. they will have to replace the fluids to check
tell them you are worried about the metal shavings in the diff like the 06's were having.... i dunno bout if they can do the tranny like that tho. it worked for my diffs tho heh. im sure you can go to your local oil change shop to have the tranny flushed. as far as i know a tranny service is a flush and replacement of the filter on the inside of the pan. pretty simple.