Compatible motherboards for Alienware 18?

So, my alienware 18 broke recently, and much to my dismay, the 1-year warranty I ordered on the day I purchased it expired on April this year.

After sending it to some local techs, the problem was deemed that the motherboard was damaged, and that it would have to be replaced. Now, I am nowhere even remotely near being a hardware person, so after some inquiry, they said I would need to find a "3FGT2" motherboard, if I wanted it to be repaired locally.

I considered sending it in for repair, but after speaking a customer service agent, I found that it would cost  little around $430 plus tax to get my problem repaired, as a loose estimate.

He also informed me that I should also try to find another motherboard, maybe for cheaper, with the label of "4703X" instead.

I'm treading into unknown territory when I search for motherboards to buy, but I would at least like to know what specific motherboard I need to fix the problem.

If more information is needed, I'll try to provide what I can.

Thanks in advance.

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