If I am understanding correctly your computer does have a service hatch, with the computer disconnected from the AC adapter do the following if you will;
Remove the main battery.
Press the power on button for 30 seconds.
Remove the service hatch.
Ground yourself by touching something like a radiator.
Press the power on button for around 30 seconds.
Remove the RAM and disconnect the CMOS battery (shown in attachment below).
Press the power on button again then leave the computer for 5 minutes or so.
Replace the CMOS battery only.
Attach the AC adaptor only.
Power up the notebook to see if the behaviour changes, any error beeps etc then get back to us please.
NB: Removing the back does not automatically void your warranty, you are normally allowed to upgrade your RAM and unless any warranty seals have been broken or damage to the notebook occurred then any warranty should still be honoured, I am not suggesting any dishonesty here but if the notebook is otherwise in good order and there is a current warranty in place you only need to take it in and explain the black screen problem, nothing more than that.