Thanks for the advice. Are you sure about this though? While scouring forums I found at least one person who claims they used an iMac as a monitor for a year after their video card died. Obviously the Mac has to be able to boot up; but provided it is the gpu and the gpu only that isn't functioning? The display is driven by the "main" mac gpu when using target display mode, right?
Also, I was reading about people who were able to start their iMac up in safe mode and reported that they didn't need the video card functioning to get this to work. This sounds much more unlikely to me but I really don't know.
I guess I will get to try it all in a week or two. Really hooooping I can use target display mode at least though.