Ignition Switch stays on when key removed?

Probably replace the ignition , probably have to be programmed also , A lock smith would probably be cheaper than the dealer if you can find one to do it .

Sounds like when you leave the car, the ignition is still in the run mode draining the battery. As you said that you can remove the key in the run position, I'd suspect that the key is worn out.

Yup, worn out key. Having the original key duplicated won't solve the problem. When you do that the original key is copied or traced to make the new key. By doing that the wear on the old key will be transferred to the new key. Either replace the ignition lock cylinder or see if the original key codes are still available from the Dealer. Since the vehicle is 18 years old the codes are probably no longer available. Hope that helps! Jim