thanks, i've always wandered what that part was called, makes it easier to explain things

 

Well I changed the plugs on my 4.0 liter 1998 Ranger. The old ones can out but they were really stuck in there. I never experienced such a tough withdrawal. They were so difficult to back out I thought they must have been cross threaded when they went in. Well I backed them out slowly and they all came out - from the top of the engine - I didn't have to go in through the wheel wells which I looked at but access would have been worse than from the top so I don;t know why anyone would try this access method. I only broke one plugs' ceramic insulator which was no big deal. This was on the drivers side #2 plug. It broke because of the spark plug socket being off center due to some sort of pipe above the exhaust manifold. I took extra care to be centered when I put the new ones in.
I put on a bit on never seize on the new plug threads and they went in nice and easy so I was glad I put some on. It will make removal much easier. I used the copper based stuff as it is supposed to be a higher heat type.
It ran a bit better but there still is a bit of pinging under heavy load - up a hill with no downshifting. Old plugs were in decent condition but it was time for a change (IMO).

 

well you have a 98 which is a different motor than the OP's 03 and going in from the wheel well on the passenger side is much easier than from the top.