Look underneath to see if there are any rust holes in the rear floor pan. (Or lift the carpet from the top) Make sure the transmission (if an Automatic) is shifting okay. Check the fluid to see if it smells burnt of is very dark. Autos for these things can be had for fairly inexpensively but are a pain to replace and there were several versions of this tranny. 68 thousand tells me that it should be okay. I recently replaced on that went 160,000. Good luck!
Junkman