For a car that old, no doubt you need new bushings -- they're incredibly cheap, a few cents each, but are needed so that the movement of the shifter produces corresponding movement in the levers actuating the internal transmission parts -- i.e., changing gears. The bushings ensure that the connections are tight, yet allow them to rotate; and if they're gone (they might have not only deteriorated but actually fell apart and off the linkage, leaving nothing but sloppily loose connections -- you move the shifter, yet little or nothing happens inside the transmission).

It's even possible that the fasteners holding the linkage together has gotten loose.

All in all, very, very cheap for the parts -- but the do-it-yourself task can be very dirty (again, age of the car suggests inevitable leaks, grease and grime) working under the car, not to mention awkward as well unless you have tall jackstands.