Different kind of headache here
 

My chick has an 01 Montero Sport that we just recovered last evening. She was just trying to help out a friend and let him borrow it for what was of course supposed to be a hot second and He'd be right back. Fast forward about a week or so and we were able to grab it back last evening. No biggie, easy peezy, but this fool still has the spare key to it and I'm telling my girl that I'm not going to sit out there every second of the day and night waiting for this friggin' lame ass individual to surface in an attempt to snatch it up. What is the best way to deal with an issue like this. Please believe the idea of sockin' him is 100% fine but I already know how fat of a chance that is. So I was wondering how hard is it to switch to different keys all the way around? Help me out fellas, ladies, anybody?

Switching the keys might be too much and too costly. Just get a steering wheel lock a.k.a. The Club or something similar. This will prevemt the vehicle from being driven away even if your "nice friend" has the car keys.