Ihave a 2006 Fx4 with 80k and I need to change the coils and the plugs, I have a very bad miss coming from cylinder 5 and 7 along with a random missfire, I replaced both of the coils and cylinder 5 is still missing and I stilll have the random miss fire, coils are no big deal to replace but spark plugs are crazy!!!any ideas how much it would cost to take it to the shop and have them do it?