I have had this problem on some of the past 5 gearboxes (I've a heavy right foot).the travel of the gearstick, when in gear, should be about half an inch or thereabouts on a good one.
please note this may be cause by the small bushing on the top of the gearbox...to find it, follow this and you'll see what I mean:
see where the gear cables go onto the gearbox, they are held in place with a small pin and a washer (this is standard with the washer, not some idiot after doing a cheap fix lol)...take off the cable, inspect the bushing in the end of the cable (POSSIBLE problem #1)
if both these cable bushings are ok and have no excessive play when conected, then check the small bushing on the gearbox hinted at above...
there is a vertical and horizontal cable on the 'box, and the horizontal cable makes the gearstick in the car move from left to right...try and take the linkage on the gearbox off, there is a small square bushing inbetween that that can also wear out (POSSIBLE problem #2)
the gear linkage in the car usually survives very well, my own car had over 300k Miles and was still fine
hope this helps