Electonic problem

Recently I had a stereo put in my 89 RX7 GTUs. When I got it back the steering was hard as crap and the rear defrost light stayed half on when the defroster was off. I drove it home thinking the belt fell off (didnt notice the defrost light till later) and when i got there I found that the belf was on and the pump had suffencet fluid. Also this pump is not old as the car. It came with my 30k mile jdm motor. So what I think happend is when he wired the stereo that he somehow messed up some wiring that had to do with the speed sensitive steering and I have no clue about the defroster. Tomorrow a friend of mine is taking my car back because i have to go to work before the place opens. I hope he can fix it. But does anybody know anything about stereos and there affect on the steering system and other electronics in the car. Thanks for you time.