Replacing Motherboard. My Gateway GT4024 desktop won't boot and monitor doesn't connect. Same

Question

My Gateway GT4024 desktop won't boot and monitor doesn't connect. Same monitor works on different PC and because the video card is part of the motherboard I assume the motherboard is broken. I took it to Geek Squad they diagnosed the same. They don't replace motherboards. So if I purchase a new motherboard (MS-7248) how hard will it be to do it myself? I'm not 100% sure that it is the motherboard but when I power it up with a new video card in it, the monitor shows Gateway but doesn't go through the boot process. The hard drive fan is running. The motherboard will cost about $200 delivered. Should I replace the motherboard or just buy a new computer?