I have 104k on it untouched so I'm sure the plugs need replaced, light had came on on our way back from Florida, immediate loss of power and sluggishness and no a/c. Getting a p0351 code, ignition coil primary/secondary curtuit. Question is I can replace the bad coil,which is from what I've read is the 1 in 351, and all the plugs or change all of the coils while I'm in there? My other question is the difference in an oem coil and say a set on eBay are the same price, $80 for one ford oem and roughly $80 for 6 aftermarket?? Thank you for your help.