1998 cavalier miss in motor-program ecm??

I am new to this forum. Hello all! 1998 Chev Cavalier has a miss in the motor, with engine light on.Engine is 2.2 litre 4 cyl.and goes well when kicked down.Also key cylinder in steering column is jammed , have to fidget with it to get it to work.
A mechanic friend has told me that I may have to get the body computer reprogrammed by GM, and that the key cylinder is hard to find in a wrecking yard . The key does not communicate with the engine computer in order to start the car.
I have never heard of this "body" computer,,Is any of this true?
Please help If you can!

Thanks , Peter