It sounds strange that wires that were so tight now have no grab at all. Do you have the little caps on the end of the plug? If the ends are somehow deformed you should be able to crimp them with some plyers to make them tight again - at least tight enough to drive a few miles to the shop. Or replacing the wires is not that tough a DIY job - just pay attention. You don't have to put all the wires back into that silly plastic channel on top of the valve cover.