I've got over 190K on mine, with me doing about 30k of that. Have you changed the tranny fluid? That would be the first thing I would do. Come to thing of it, I should probably check to see if I did that on this one since I bought it.
I believe they changed the 'seal' between the shifter and the tranny due to this occurring. Some have removed the shifter and cut away some of the old gasket/seal. I would just replace it if I went that far though, lol. The early models also seemed to have trouble with teeth breaking off. That's just stuff I found when I had my NSG370.