Motherboards for laptops are unique one of a kind items. You will not be able to swap in any other one except from a G62-300 series laptop. You can salvage the RAM but there is no video card to save; it is part of the motherboard. Odds are the only bad component is the motherboard and the processor is still good despite the blink codes. This is the part number for your motherboard:
592809–001
Here is one on eBay:
Here is the Service Manual showing how to do the replacement:
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