Alright, in the Slot that your Gpu is in there should be a small clip/button/lever somewhere (often on the right side of the socket) Press that and the Gpu should slide out with probably a small amount of resistance, but nothing drastic.
When you start to boot (the moment you press the power button) Tap F8 until it brings you to a screen with options, then select safemode with networking.
Use your antivirus to scan for viruses, Install malwarebytes and do a full scan to check for malware.
Memtest86 is a free program that is easy to use and will run a test on your Ram to see if it's working correctly.
In addition try installing a program called HWmonitor, this shows what temperatures your hardware is running at.
Hope this helps.