2004 Chrysler PT Cruiser - warning lights

my father had the problem of the car stalling and they told him to clean up the computer it had some dust, after he did this it stopped and havent had that problem again it runs smoothly, but now the light on the oil change turns on, he already did oil change and transmission oil change and the lght continues to turn on, also the beeping of the seat belt keeps going off, but no light telling him whats the matter. if anyone please let me know thank you

Would your dad be willing to tell us exactly what he did?
Cleaning up the computer because it had some dust suggests to me that there’s been a miscommunication somewhere along the line. The “computer” is a sealed unit.

The oil change reminder has to be reset after the oil is changed. The procedure is in the owners manual, I no longer remember the steps.