Hi,
Replacing only the parts won't solve anything, or if it does it'll only solve it for a short while.
The whole phone logic board needs cleaning, you would need to disassemble the phone, and then clean the logic board with 99.9% isopropyl alcohol and a toothbrush, you can also put it in a small tub of isopropyl alcohol whilst cleaning it, this is a DIY solution.
Then you could try replacing parts.
Or take it to a professional with an ultrasonic cleaner. :-)