I can confirm Augustine a depleted CMOS battery will not cause much issues to your systems. But check at first RAM and HDD then the BIOS can be corrupted if so you have to flash it. The 3rd possibility is the graphic chip can cause this issue and the 4th possibility is a damage in mainboard.
will be a lot more expensive. If you buy ALL parts from a car and assembled by your self it will be 10 times expensive than to buy an already assembled car. The same is for smartphones.