There's a "finger" at the very bottom of the shift lever. It fits in the slot formed by a sliding "fork". If you've got first and reverse, the finger is probably still good. More likely a fork or forks for 2nd/3rd has slid out of reach of the fork. Either way, undo the bolts holding the cover plate to the housing. Make sure you remember which gear position the lever was in before removing. The whole thing - plate and levers - can be pulled straight up. At that point you can get a good look at both the shift lever finger and the sliding forks.
//greg//