F801s nikon focusing

Question

Hi, I have this camera for a long time buthave been used only for a few times (less than 30 rolls of films). I remember to have loaded this camera with a battery in reverse (just 1 of them). After this, I realize I could not get proper focusing anymore on AF. I am using a Nikon 28-80mm AF lens. If I could be able to identify the faulty part, I could buy a second hand F801s and try swap it. Can you help try which part is broken for this matter? Thanks.

Dexter Faustino