yes you can wiggle it back and forth (the pitman arm) and yo ucan stick some pliers on teh input shaft and "feel" the play. you can also tighten the preload on them with the set screw on top.... check to see that some threads on it are still exposed and chances are it has never been tightened. One of my boxes has the top of the set screw even with the nut and it still works great though....
the key is to tighten it up to where it dosent bind at the extremes... if it is worn it won't be tight in the middle after that. They are all a little looser in the middle so don't freak out.
They are also easy to rebuild if it leaks. Kits are available at autozone or rock auto or wherever.
I believe Jim offers a warranty also so if you get it home and it sucks you can go swap it for another.