It is most likely rusted
It is a simple leaver
I would try and access it from below
And give it a good squirt of penatrateing oil
Otherwise you have to open up the console
I had a 90 and it had the same problem
Assuming it is an auto box, put it in P and have somebody rock the car back and forth why you gently but firmly apply pressure to the hi-low lever. Like most mine was stuck/stiff but moved with some back and forth rocking pressure on the gears.