have you confirmed that it's the motherboard fault?
have you checked that the AC adapter is working?
have you tried powering on without the battery and just AC power?
If yes and all is pointing to an internal fault you will need to take the baby apart and examine the board. If it's an easy fix then you're in luck, but if the board is deep fried (it's not a surface problem and you won't be able to fix it yourself without advanced tools) I think you'd be better off getting a new laptop.
As far as taking the laptop apart is concerned, see this very nice guide here: http://www.tomshardware.com/forum/53660-35-notebook-lap...
also I'd recommend to find you laptop's manual published by the manufacturer, most often they list all the screws that are used to hold the case toghether, so it will make it easier to locate and take screws out.