how do i change the spark plugs
Get some experienced help or take it to a mechanic. You do not have the knowledge or experience to do this yourself.
Do them one at a time. Unplug the coil and then remove the coil by removing the bolt that holds it on. Remove the spark plugs and install new ones with anti-seize on the threads. Use dielectric grease on the coil boot rubber mating surfaces to seal out moisture, install coil, re-install the small bolt and plug the coil in.
Bob is right that this is a job for an experienced mechanic.
Using penetrating oil on the plugs before removing may be a good idea and can help avoid stripping the threads. Soak over night for best results.
Looking for a Used Grand Marquis in your area?
CarGurus has 3 nationwide Grand Marquis listings and the tools to find you a great deal.
Search Mercury Grand Marquis Questions
Mercury Grand Marquis Experts
Related Models For Sale
Used Cars For Sale