This vga is on your motherboard, but you do not have to replace anything. Just get a classic discrete graphics card and install it. Then you can disable the onboard vga in BIOS so that it does not take any resources any more, like your main RAM, which it uses for its video memory.
By the way, you cannot be sure that the monitor is ok. Maybe it is the monitor, not vga. Test the monitor with another computernto check whether or not this happens there as well.