Q: How to change sparkplugs? 1997 Cadillac Eldorado

Hi there - your first move would be to carefully sketch or cellphone camera record each coil position, then removed the coil packs. Using a spray tube, hose down the spark plugs with rust penetrant (WD-40, PB Blaster or similar), then go to the beach for a week. Seriously! Then carefully use a spark plug socket, and attempt to unscrew each plug. A 3/8" electric impact tool is an excellent way to remove these (no air wrenches!) - small shocks to break the plugs loose without stripping the threads. Waiting for the penetrant to do it’s work is key here! If you strip the threads, a thread insert repair will be necessary (aluminum heads for the Northstar V8s). For professional assistance, I recommend spark plug replacement performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, and make this repair for you.