Leeeoooooo

Hmmm, sounds like my problem... (88 push button 4wd DL Wagon) Started two days ago, louder when I step on the clutch, sounds a little different in any gear, changes with speed of the vehicle, not the engine. I was guessing the fluid may be low, but the guy at the oil change place says he can't check it because it's a complicated process involving the speedometer and they aren't set up like a shop. He said he does see signs of a slight leak. Chilton's says just check the dipstick to the left of the engine oil dipstick. I don't see this second dipstick. Can the guy from the oil change place be right? How can I check/add manual transmission fluid? -Leo!