Help

I took my Acer computer to the repair guy after several blue screens and then..no boot-up...no beep. He says he tried replacing everything but it still won't come on, that maybe brown outs or something must of ruined the motherboard because that's the only thing he didn't try. I over heard him say it wouldn't be worth it to fix it. The computer is only 15 months old and I paid almost $500.00 for it at newegg. My daughter says she can replace the motherboard but how do I go about finding one with all the right specs?
I'm not computer illiterate, but this is a little over my head. Tammi

thank you saint19. I will give them a try. Tammi