I just bought an 02 MPV and when I turn the key to turn it off it stays on. Also I can take the key out and it still stays on. My Over Drive off light stay on and won't come off. So I cant put it in overdrive. Does some one have any suggestions about these problems I'm having.

 

The one issue with the key-switch could be local to the actual switch unit. The fact that you also have a problem with your OD switch leads me to suspect a more extensive wiring harness issue somwhere in your steering column.

 

It can also be transmission. If the transmission switch thinks the gear is not in park, it will not de-energize the lock solenoid (safety feature). This is often related to that damned cable linkage between the shift console and the switch on the transmission itself; with wear, the indexing goes out of adjustment. If this is the case (and I hope it is), it's an easy re-adjustment.
Just add this one to the other 67,942 reasons why not to buy vehicles with automatic transmissions