How can I remove a plank from the middle of the field?
If you really want to try to save the plank, BMitch's instructions for removal are spot on but instead of a circular saw, get yourself one of these babies:



The square blade shown here will give you clean end cuts, and for your long run, this blade will be your friend:


You'll get very straight, TIGHT cut lines along the seams, be practically invisible when all is back in place.