Am I Struggling with a I/O Board Issue, a Logic Board Issue, or...?

I have a beautiful MPB Mid-2012 Retina that has thrown unexpected temper tantrums up until the point where the Mac will not start. It originally shut it down a couple of times when on battery power and plugging it in would calm its nerves and bring the unexpected shutdowns to a stop. However after a week of keeping him on power he quite suddenly stopped booting. When I plug his mag safe cable in, the green light appears to show that the battery is charged, but he no longer responds to my attempted start-ups. He did, at one point, start his fans in the middle of the night, which scared me to death since my desk is in my room, but beyond that he has been mostly-dead.

What should my next steps be? Just like the Princess Bride, is my Mac somewhat alive? Was he just trying to breathe out the words true love and am I missing it as to blave? Or have I just beat this analogy dead and there is no hope?

The Apple store was absolutely no luck and simply recommended a new computer (Sad, because I think there is a great deal of life still in this mac: There isn’t a single scratch on him). I have repaired motherboards on other’s Macs before, so I am not afraid to make it happen, but I would like to verify that the issue isn’t something smaller before I blow the cash.

The iFixit community has never let me down before, so here’s to you guys! Let the advice rain and thanks for your help in advance.