Dieseldatsun

Just purchased a 1982 diesel 720 long bed a couple of weeks ago. First thing I noticed when I opened the door is that it smells like transmission fluid in the cabin. I was driving it on the highway a few days after I bought it, and the speedometer just quit on me. Then I noticed that the odometer was just barely crawling forward. I've finally had time to get behind the instrument panel today (my first time there), and I can see why the cab smells like tranny fluid and the speedometer and odometer aren't working and all the problems have the same source. There's tranny fluid leaking out of my speedometer cable. Probably has been for a while. Could it have just been a loose connection? Or do I need to replace the cable? If so, how?