Not hard at all. In fact, it's almost fun. Your spark plugs are located right on top of your engine under that plastic cover. Use an Allen wrench to remove the cover and voila! Your plugs are right there. Use a ignition wire boot removal pliers to pull the boots free of the plugs. Then a 3/8 socket handle with an extension connected to a spark plug socket is used to remove the plugs. Righty tighty-lefty loosey! Gap the new plugs according the specifications in the owners manual using a gaping tool. Smear a little anti-seize on the each plug's threads and thread the plugs into their holes by hand. never use the wrench. Only after the plugs are hand tight do you snug them down gently with the wrench. Not too tight! Replace the ignition wires to their respective plugs, replace the top cover and you are done!!!
How to change the spark plugs
Both V6 engines have 6 spark plugs
they are located in the engine block. You'll need an extension to the wrench in order to get them out.
Disconnect the battery, remove the spark plug cables and boots, and remove the old spark plugs. Put in the new spark plugs, attach the boots and cables, and connect the battery.
It is moderately easy to change the spark plugs on a Liberty, although it is rather tricky because of the gap between the spark plugs.
Sell it !!!
take off the plastic cover and under where the silver cover on the engine says ecotech is where the spark plugs are located
there are 3 in the front and 3 in the back if its a 6cyl.
Spark plugs and wires
Changing spark plugs is relatively easy. Disconnect the batter and spark plug cables, and remove the old spark plugs. Next replace the spark plugs with new ones, reconnect the spark plug cables and battery.
Have a look at ; www.carbasics.co.uk
This is for the '05 Frontier, but should be what you're looking for. http://www.clubfrontier.org/forums/f23/how-change-spark-plugs-2005-gen-2-frontier-40507/