I had a coil go out on me this past spring. Had it replaced, although before that there was the mis-diagnosis. I digress. Later, I discussed with a Ford dealer, changing them all out and I was advised that considering the cost, here in Canada, in a shop, make that about $1,500. V-10, 10 coils at about $90.00 a pop plus install, to not do it.
I have subsequently purchased a scanner from O'Rielly and one extra coil at a mid-range US pricing. The scanner will tell me if it is a coil, if there is a next time, not something other...like a fuel pump, for instance.
Gary Haupt