I need motherboard circuit diagram to fix a faulty mosfet transistor

I doubt anyone will have a schematic for this board.

Beyond that, since the boards cost as little as $100-150, it's not really worth repairing this one -- by the time you buy a donor board once you identify the faulty part (just about the only way you'll source a replacement MOSFET), you still have no way of knowing why the failure occurred, or whether replacing a single chip will actually fix the problem.

It does not even cost that much.  A whole machine can be had for less than $40 USD at the time of this post.  Including motherboard, power supply, chassis and cable/adapter.  The seller in example link provides free shipping, free return, and 30 days warranty. 

By obtaining schematics, it does not resolve the issue.  ALL computer makers warranty would replace the boards.  They don't repair them.