you don,t really need 2 hdmi inputs for a monitor just 1 for the 360 and a dvi for the pc. you can also buy a vga cable for the 360 from monster cable, (vga for picture and rca for sound)
You can get a TV tuner card for you pc. they come in usb and pci, pci-e flavors. Then depending on what your monitor has available you could use the 360 VGA cable or HDMI cable.