When I boot my computer some times the monitor fails to display. I have had the monitor checked and since I have both DMI and VGA connections I was told to switch from DVI to VGA. This seemed to work for some time but then it started all over again. I think it is the VGA card but I don't know if I can just replace the VGA card or if it is hard wired to the motherboard must I replace the motherboard also?
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.
It may very well be a motherboard problem. It's rare that JUST the integrated video goes bad on a motherboard and everything else is fine. Very rare. You're looking at having to replace the motherboard. If you're made of money, you can buy a PCIe graphics card and run video through that instead. If and when the motherboard fails, you'll have to replace that.