If you have a 4cyl. they will be inside the valve cover. There will be round rubber plug wires that go in on top of the valve cover. They are in the same place if you have coil packs. Just pull the wire or coil pack out and look into the hole and there is your spark plug.
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/
How to change the spark plugs
On the sides of the engine connected to the spark plugs... Ask any one that's not dumb
NGK platinum plugs
It can be complicacated since on some models the spark plugs are difficult to get to but I would recommend to find the spark plugs first and then double check to make sure you know where they are.
Both V6 engines have 6 spark plugs
yes - 8 spark plugs for a gas V8 engine
( 6 ) spark plugs
how calibrate spark pulg for suzuky verona 2005?
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.
factory recomends every 30,000 miles or 60,000 if you are running platinum plugs.
I would replace the spark plugs after 50K, the wires and plugs again at 100K.