a problem with the graphics card, or the cable to the monitor. (In my experience, the cable is the likely culprit!)
I'm assuming you don't even get to see the BIOS stuff doing it's check during startup??
The easiest thing would be to see if you can borrow/swap a monitor and a cable. If you still can't see anything it suggests the grahics card is where the problem lies.
The process of changing a grahics card is quite easy... providing you do actually have a seperate card and not "onboard" graphics, (which is where the graphics card is built into the motherboard).
See if you can arrange a temporary swap first, and report back.