Definately sounds like he has potential.

If you want to get him to the point where he behaives well during out time, I reccomend having his wings clipped. If he isn't used to stepping up or staying in one area when outside of his cage, he may get himself into trouble. Parrots are pretty good about that!
Have you owned any birds before? Just wondering if you know the basics(such as no spraying air freshners, hairspray, etc. around birds.. and so on).

Good luck and keep us updated! African Greys sure are a treasure to have.